diff --git a/.gitignore b/.gitignore
index f6e247d..d97dcac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,9 @@ backend/data/
 *.db
 *.db-journal
 
+# DB-Backups (enthalten personenbezogene Daten — niemals ins Repo)
+backups/
+
 # Build artifacts
 frontend/dist/
 dist/
diff --git a/backend/db.js b/backend/db.js
index 1dad4f6..8e2ddbd 100644
--- a/backend/db.js
+++ b/backend/db.js
@@ -68,12 +68,20 @@ if (usePostgres) {
     },
 
     transaction(fn) {
+      // H2: Transaktions-Contract — fn erhält eine txDb-Instanz, deren
+      // prepare()-Statements auf DERSELBEN Connection laufen wie die Transaktion.
+      // WICHTIG: Alle Statements innerhalb von fn MÜSSEN über txDb.prepare()
+      // erzeugt werden. Statements, die außerhalb (über das globale db-Objekt)
+      // vorbereitet wurden, laufen außerhalb der Transaktion und machen sie
+      // wirkungslos (kein Rollback bei Fehlern).
       return async (...args) => {
         const client = await pool.connect();
         try {
           await client.query('BEGIN');
-          
+
           const txDb = {
+            _type: 'postgres',
+            _inTransaction: true,
             prepare(sql) {
               const pgSql = convertPlaceholders(sql);
               return {
@@ -117,6 +125,12 @@ if (usePostgres) {
 
   console.log('[DB] SQLite-Datenbank verbunden (better-sqlite3, WAL-Modus, async-Wrapper).');
 
+  // H2: GLOBALER Transaktions-Mutex — SQLite hat nur EINE Connection, daher
+  // dürfen sich nie zwei Transaktionen überlappen (auch nicht verschiedene
+  // transaction()-Wrapper wie createTask + updateTemplate). Ein pro-Wrapper
+  // Mutex würde "cannot start a transaction within a transaction" ermöglichen.
+  let sqliteTxQueue = Promise.resolve();
+
   db = {
     _type: 'sqlite',
 
@@ -140,8 +154,52 @@ if (usePostgres) {
     },
 
     transaction(fn) {
-      const tx = sqliteDb.transaction(fn);
-      return (...args) => Promise.resolve(tx(...args));
+      // H2: Transaktions-Contract (siehe PostgreSQL-Modus) — fn erhält eine
+      // txDb-Instanz, deren Statements innerhalb der Transaktion laufen.
+      // better-sqlite3's transaction() ist synchron; die async fn wird über
+      // den GLOBALEN Warteschlangen-Mutex serialisiert (siehe oben).
+      return (...args) => {
+        const run = async () => {
+          const txDb = {
+            _type: 'sqlite',
+            _inTransaction: true,
+            prepare(sql) {
+              const stmt = sqliteDb.prepare(sql);
+              return {
+                run: (...params) => Promise.resolve(stmt.run(...params)),
+                get: (...params) => Promise.resolve(stmt.get(...params)),
+                all: (...params) => Promise.resolve(stmt.all(...params)),
+              };
+            },
+            exec(sql) {
+              sqliteDb.exec(sql);
+              return Promise.resolve();
+            },
+            pragma(str) {
+              sqliteDb.pragma(str);
+              return Promise.resolve({});
+            },
+          };
+          // BEGIN IMMEDIATE sichert den Schreib-Lock für die gesamte Transaktion.
+          // busy_timeout verhindert SQLITE_BUSY bei konkurrierenden Lesern (WAL).
+          sqliteDb.pragma('busy_timeout = 5000');
+          sqliteDb.exec('BEGIN IMMEDIATE');
+          try {
+            const result = await fn.call(txDb, ...args);
+            sqliteDb.exec('COMMIT');
+            return result;
+          } catch (err) {
+            try { sqliteDb.exec('ROLLBACK'); } catch (rollbackErr) {
+              console.error('[DB] Rollback-Fehler:', rollbackErr.message);
+            }
+            throw err;
+          }
+        };
+        const result = sqliteTxQueue.then(run, run);
+        // Queue darf nie in einem Fehlerzustand hängen bleiben
+        sqliteTxQueue = result.catch(() => {});
+        return result;
+      };
     },
 
     close() {
diff --git a/backend/ldapSync.js b/backend/ldapSync.js
index 8a1e1ae..077d122 100644
--- a/backend/ldapSync.js
+++ b/backend/ldapSync.js
@@ -18,8 +18,15 @@ const { Client } = require('ldapts');
  *   LDAP_BIND_USER         - Service account in user@domain.fqdn format
  *   LDAP_BIND_PASSWORD     - Password for the service account
  *   LDAP_SYNC_INTERVAL     - Sync interval in ms (default: 300000 = 5 min)
- *   LDAP_FILTER            - Custom LDAP filter (default: active users)
+ *   LDAP_FILTER            - Custom LDAP filter (default: active user accounts only —
+ *                            excludes computers, service accounts (sa_*), trust accounts
+ *                            and the built-in Administrator/Gast)
  *   LDAP_ATTRIBUTES        - Comma-separated LDAP attributes
+ *
+ * Rollen (Fix 2, überarbeitet): Rollen werden AUSSCHLIESSLICH über die App
+ * verwaltet (Nutzerverwaltung). Der Sync legt neue User immer als 'user' an
+ * und ändert die Rolle bestehender User NIE — AD-Gruppen fließen nicht in
+ * App-Rechte ein.
  */
 
 const LDAP_SERVER = process.env.LDAP_SERVER || '';
@@ -30,7 +37,16 @@ const LDAP_IGNORE_CERT_ERRORS = (process.env.LDAP_IGNORE_CERT_ERRORS || 'false')
 const LDAP_BIND_USER = process.env.LDAP_BIND_USER || '';
 const LDAP_BIND_PASSWORD = process.env.LDAP_BIND_PASSWORD || '';
 const LDAP_SYNC_INTERVAL = parseInt(process.env.LDAP_SYNC_INTERVAL) || 300000;
-const LDAP_FILTER = process.env.LDAP_FILTER || '(&(objectClass=user)(!(userAccountControl:1.2.840.113556.1.4.803:=2)))';
+// Fix 1: Standard-Filter nur echte Benutzerkonten — keine Computer ($), keine
+// Service-Accounts (sa_*), keine Trust-Accounts, nicht deaktivierte Konten.
+// 1.2.840.113556.1.4.803 = LDAP_MATCHING_RULE_BIT_AND (userAccountControl-Bits)
+// Bit 2 = ACCOUNTDISABLE, Bit 512 = NORMAL_ACCOUNT (nur echte Benutzerkonten
+// haben dieses Bit; Computer = 4096, Domain-Controller = 8192 haben es NICHT).
+const LDAP_FILTER = process.env.LDAP_FILTER
+  || '(&(objectClass=user)(sAMAccountName=*)(!(sAMAccountName=*$))(!(sAMAccountName=sa_*))'
+     + '(!(sAMAccountName=Administrator))(!(sAMAccountName=Gast))'
+     + '(!(userAccountControl:1.2.840.113556.1.4.803:=2))'
+     + '(userAccountControl:1.2.840.113556.1.4.803:=512))';
 const LDAP_ATTRIBUTES = (process.env.LDAP_ATTRIBUTES || 'mail,displayName,memberOf,distinguishedName,sAMAccountName').split(',').map(a => a.trim());
 
 let syncTimer = null;
@@ -40,16 +56,6 @@ function isLDAPConfigured() {
   return !!(LDAP_SERVER && LDAP_SEARCH_BASE && LDAP_BIND_USER && LDAP_BIND_PASSWORD);
 }
 
-function extractRole(memberOf) {
-  if (!memberOf) return 'user';
-  const groups = Array.isArray(memberOf) ? memberOf : [memberOf];
-  const groupStrings = groups.map(g => String(g).toLowerCase());
-  if (groupStrings.some(g => g.includes('admin') || g.includes('domain admins') || g.includes('domänen-admins'))) {
-    return 'admin';
-  }
-  return 'user';
-}
-
 async function syncLDAPUsers(db) {
   if (!isLDAPConfigured()) {
     console.log('[LDAP] Nicht konfiguriert - LDAP-Sync deaktiviert.');
@@ -92,12 +98,10 @@ async function syncLDAPUsers(db) {
       const rawCn = Array.isArray(entry.cn) ? entry.cn[0] : entry.cn;
       const rawDN = Array.isArray(entry.distinguishedName) ? entry.distinguishedName[0] : entry.distinguishedName;
       const rawSAM = Array.isArray(entry.sAMAccountName) ? entry.sAMAccountName[0] : entry.sAMAccountName;
-      const rawMemberOf = Array.isArray(entry.memberOf) ? entry.memberOf : (entry.memberOf ? [entry.memberOf] : []);
 
       const email = (rawMail || '').toLowerCase().trim();
       const name = rawName || rawCn || '';
       const distinguishedName = rawDN || '';
-      const memberOf = rawMemberOf;
       const username = (rawSAM || '').trim();
 
       if (!email && !username) continue; // Skip users without email AND username
@@ -105,7 +109,6 @@ async function syncLDAPUsers(db) {
       adUsers.push({
         email: email || (username + '@ad.local'),
         name,
-        role: extractRole(memberOf),
         distinguishedName,
         username,
       });
@@ -121,23 +124,46 @@ async function syncLDAPUsers(db) {
     let inserted = 0;
     let updated = 0;
 
-    const insertStmt = db.prepare('INSERT INTO users (email, password, name, role, status, source, username) VALUES (?, ?, ?, ?, \'inaktiv\', \'ad\', ?)');
-    const updateStmt = db.prepare('UPDATE users SET name = ?, username = ?, role = ? WHERE id = ?');
+    // H2: Statements innerhalb der Transaktion über txDb erzeugen.
+    // WICHTIG (PostgreSQL): Ein UNIQUE-Verstoß bricht die GESAMTE Transaktion
+    // ab ("current transaction is aborted") — ein try/catch um den Insert
+    // hilft dort nicht. Daher werden Kollisionen VOR dem Insert per SELECT
+    // erkannt (ON CONFLICT wäre die Alternative, ist aber im gemeinsamen
+    // SQLite/PG-SQL-Dialekt nicht portabel).
+    const syncTransaction = db.transaction(async function () {
+      const txDb = this;
+      // Rollen werden app-seitig verwaltet: neue User immer 'user', bestehende
+      // User behalten ihre in der App gesetzte Rolle (Sync fasst role nie an).
+      const insertStmt = txDb.prepare('INSERT INTO users (email, password, name, role, status, source, username) VALUES (?, ?, ?, \'user\', \'inaktiv\', \'ad\', ?)');
+      const updateStmt = txDb.prepare('UPDATE users SET name = ?, username = ? WHERE id = ?');
+      const emailExistsStmt = txDb.prepare('SELECT id FROM users WHERE LOWER(email) = LOWER(?)');
+      const usernameExistsStmt = txDb.prepare('SELECT id FROM users WHERE LOWER(username) = LOWER(?)');
 
-    const syncTransaction = db.transaction(async () => {
       for (const adUser of adUsers) {
         const existing = existingMap[adUser.email];
         if (existing) {
-          await updateStmt.run(adUser.name, adUser.username, adUser.role, existing.id);
+          await updateStmt.run(adUser.name, adUser.username, existing.id);
           updated++;
           delete existingMap[adUser.email];
         } else {
+          // Kollisions-Precheck: E-Mail oder Username bereits belegt?
+          const emailTaken = await emailExistsStmt.get(adUser.email);
+          if (emailTaken) {
+            console.warn('[LDAP] E-Mail bereits vorhanden:', adUser.email);
+            continue;
+          }
+          const usernameTaken = adUser.username ? await usernameExistsStmt.get(adUser.username) : null;
+          if (usernameTaken) {
+            console.warn('[LDAP] Username bereits vorhanden:', adUser.username);
+            continue;
+          }
           try {
-            await insertStmt.run(adUser.email, 'LDAP_AUTH', adUser.name, adUser.role, adUser.username);
+            await insertStmt.run(adUser.email, 'LDAP_AUTH', adUser.name, adUser.username);
             inserted++;
           } catch (err) {
-            if (err.message && err.message.includes('UNIQUE constraint') || err.message?.includes('duplicate key')) {
-              console.warn('[LDAP] E-Mail bereits vorhanden:', adUser.email);
+            // Fallback für Race-Conditions zwischen Precheck und Insert
+            if (err.message?.includes('UNIQUE constraint') || err.message?.includes('duplicate key')) {
+              console.warn('[LDAP] E-Mail bereits vorhanden (Race):', adUser.email);
             } else {
               console.error('[LDAP] Insert-Fehler:', err.message);
             }
@@ -151,17 +177,50 @@ async function syncLDAPUsers(db) {
     // Remove stale AD users
     const adEmails = adUsers.map(u => u.email.toLowerCase());
     const toRemove = existingRows.filter(r => !adEmails.includes(r.email.toLowerCase()));
+
+    // H3: Mass-deletion protection — a single failed/empty LDAP result must not
+    // wipe the entire AD user base (and their tasks via ON DELETE CASCADE).
+    // Abort the sync if we would remove more than LDAP_MAX_DELETE_PCT (default 25%)
+    // of the currently known AD users, or if the LDAP search returned zero entries.
+    const LDAP_MAX_DELETE_PCT = parseInt(process.env.LDAP_MAX_DELETE_PCT) || 25;
     let removed = 0;
     if (toRemove.length > 0) {
-      const removeIds = toRemove.map(r => r.id).filter(id => Number.isInteger(id));
-      if (removeIds.length > 0) {
-        const placeholders = removeIds.map(() => '?').join(',');
-        await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...removeIds);
-        removed = removeIds.length;
+      if (adUsers.length === 0) {
+        console.warn('[LDAP] Sync lieferte 0 Nutzer — Löschen abgebrochen (Schutz gegen Massenlöschung).');
+      } else {
+        const deleteRatio = (toRemove.length / existingRows.length) * 100;
+        if (deleteRatio > LDAP_MAX_DELETE_PCT) {
+          console.warn(`[LDAP] ${toRemove.length} von ${existingRows.length} AD-Nutzern würden gelöscht werden (${deleteRatio.toFixed(1)}% > ${LDAP_MAX_DELETE_PCT}% Schwellwert) — Löschen abgebrochen.`);
+        } else {
+          const removeIds = toRemove.map(r => r.id).filter(id => Number.isInteger(id));
+          if (removeIds.length > 0) {
+            const placeholders = removeIds.map(() => '?').join(',');
+            await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...removeIds);
+            removed = removeIds.length;
+          }
+        }
       }
     }
 
     console.log('[LDAP] Sync abgeschlossen: ' + inserted + ' neu, ' + updated + ' aktualisiert, ' + removed + ' entfernt');
+
+    // Fix 1 (Cleanup): Bereits kontaminierte Konten entfernen — Computer-Accounts
+    // ($-Suffix), Service-Accounts (sa_*) und der eingebaute Administrator/Gast.
+    // Diese sollten laut geschärftem Filter nie mehr gesynct werden; der Cleanup
+    // räumt Bestände auf, die vor dem Fix angelegt wurden. Läuft nur, wenn der
+    // Standard-Filter aktiv ist (bei Custom-Filter entscheidet der Betreiber).
+    const isDefaultFilter = !process.env.LDAP_FILTER;
+    if (isDefaultFilter) {
+      const junkRows = await db.prepare(
+        `SELECT id FROM users WHERE source = 'ad' AND (username LIKE '%$' OR username LIKE 'sa\\_%' ESCAPE '\\' OR LOWER(username) IN ('administrator', 'gast'))`
+      ).all();
+      const cleanupIds = junkRows.map(r => r.id).filter(id => Number.isInteger(id));
+      if (cleanupIds.length > 0) {
+        const placeholders = cleanupIds.map(() => '?').join(',');
+        const del = await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...cleanupIds);
+        console.log('[LDAP] Cleanup: ' + del.changes + ' Computer-/Service-Accounts entfernt.');
+      }
+    }
   } catch (err) {
     console.error('[LDAP] Sync-Fehler:', err.message);
   } finally {
diff --git a/backend/middleware/auth.js b/backend/middleware/auth.js
index 06819f7..0049686 100644
--- a/backend/middleware/auth.js
+++ b/backend/middleware/auth.js
@@ -9,7 +9,17 @@ const db = require('../db');
 const { auditLog } = require('../auditLog');
 
 // P6: Cookie config - defined early for use in CSRF and auth cookies
+// M1: Cookie security is now configurable via COOKIE_SECURE env var so that
+// plain-HTTP deployments (e.g. behind a TLS-terminating proxy that sets
+// X-Forwarded-Proto) can still use secure cookies, while HTTP-only dev/test
+// setups can disable them. Defaults to NODE_ENV === 'production'.
+//   COOKIE_SECURE=true   → always secure
+//   COOKIE_SECURE=false  → never secure (HTTP dev)
+//   unset                → secure in production, lax in development
 const isProduction = process.env.NODE_ENV === 'production';
+const COOKIE_SECURE = process.env.COOKIE_SECURE !== undefined
+  ? process.env.COOKIE_SECURE === 'true'
+  : isProduction;
 const COOKIE_NAME = 'workflow_token';
 
 function hashToken(token) {
@@ -24,7 +34,18 @@ const CSRF_HEADER_NAME = 'x-csrf-token';
 // Advantage: cookie and header can never drift apart (no more stale-token 403s),
 // works across tabs, page reloads and re-logins. The cookie is self-healed by
 // authMiddleware on every request if it is missing or out of sync.
-const CSRF_SECRET = process.env.SESSION_SECRET || 'workflow-portal-csrf-v1';
+// M2: Fail-fast in production if SESSION_SECRET is missing — a hardcoded
+// fallback secret in the source tree is a security risk.
+const SESSION_SECRET = process.env.SESSION_SECRET || '';
+if (!SESSION_SECRET) {
+  if (process.env.NODE_ENV === 'production') {
+    console.error('[FATAL] SESSION_SECRET Umgebungsvariable ist in der Produktion nicht gesetzt. Setze sie auf einen langen, zufälligen Wert.');
+    process.exit(1);
+  } else {
+    console.warn('[WARN] SESSION_SECRET nicht gesetzt — verwende unsicheren Fallback nur für die Entwicklung.');
+  }
+}
+const CSRF_SECRET = SESSION_SECRET || 'workflow-portal-csrf-dev-only-fallback';
 
 function deriveCSRFToken(tokenHash) {
   return crypto.createHmac('sha256', CSRF_SECRET).update(tokenHash).digest('hex');
@@ -36,7 +57,7 @@ function setCSRFCookie(res, tokenHash) {
   const csrfToken = tokenHash ? deriveCSRFToken(tokenHash) : crypto.randomBytes(32).toString('hex');
   res.cookie(CSRF_COOKIE_NAME, csrfToken, {
     httpOnly: false, // Must be readable by JS to send back in header
-    secure: isProduction,
+    secure: COOKIE_SECURE,
     sameSite: isProduction ? 'strict' : 'lax',
     maxAge: 24 * 60 * 60 * 1000, // 24h (re-set by authMiddleware on every request)
     path: '/',
@@ -65,7 +86,7 @@ function csrfMiddleware(req, res, next) {
   if (req.tokenHash && cookieToken !== deriveCSRFToken(req.tokenHash)) {
     res.cookie(CSRF_COOKIE_NAME, deriveCSRFToken(req.tokenHash), {
       httpOnly: false,
-      secure: isProduction,
+      secure: COOKIE_SECURE,
       sameSite: isProduction ? 'strict' : 'lax',
       maxAge: 24 * 60 * 60 * 1000,
       path: '/',
@@ -99,7 +120,7 @@ async function authMiddleware(req, res, next) {
   if (['GET', 'HEAD', 'OPTIONS'].includes(req.method)) {
     res.cookie(CSRF_COOKIE_NAME, deriveCSRFToken(tokenHash), {
       httpOnly: false,
-      secure: isProduction,
+      secure: COOKIE_SECURE,
       sameSite: isProduction ? 'strict' : 'lax',
       maxAge: 24 * 60 * 60 * 1000,
       path: '/',
@@ -141,12 +162,12 @@ async function createSession(userId, oldRawToken) {
   return rawToken;
 }
 
-async function deleteSession(rawToken) {
+async function deleteSession(rawToken, req) {
   if (!rawToken) return;
   const tokenHash = hashToken(rawToken);
   const session = await db.prepare('SELECT user_id FROM sessions WHERE token = ?').get(tokenHash);
   if (session) {
-    auditLog(session.user_id, 'logout', 'user', session.user_id, null);
+    auditLog(session.user_id, 'logout', 'user', session.user_id, null, req);
   }
   await db.prepare('DELETE FROM sessions WHERE token = ?').run(tokenHash);
 }
@@ -190,7 +211,7 @@ function setAuthCookie(res, token) {
   const ttlHours = parseInt(process.env.SESSION_TTL_HOURS) || 168;
   res.cookie(COOKIE_NAME, token, {
     httpOnly: true,
-    secure: isProduction,
+    secure: COOKIE_SECURE,
     sameSite: isProduction ? 'strict' : 'lax',
     maxAge: ttlHours * 60 * 60 * 1000,
     path: '/',
@@ -204,6 +225,6 @@ function clearAuthCookie(res) {
 module.exports = { 
   authMiddleware, adminMiddleware, createSession, deleteSession, invalidateUserSessions, hashToken,
   isAccountLocked, recordFailedLogin, recordSuccessfulLogin,
-  setAuthCookie, clearAuthCookie, COOKIE_NAME,
+  setAuthCookie, clearAuthCookie, COOKIE_NAME, COOKIE_SECURE,
   setCSRFCookie, csrfMiddleware, CSRF_COOKIE_NAME, CSRF_HEADER_NAME
 };
\ No newline at end of file
diff --git a/backend/middleware/rateLimit.js b/backend/middleware/rateLimit.js
index 2500a85..39f41d2 100644
--- a/backend/middleware/rateLimit.js
+++ b/backend/middleware/rateLimit.js
@@ -23,6 +23,16 @@ const loginLimiter = rateLimit({
   message: { error: 'Zu viele Anmeldeversuche. Bitte in 1 Minute erneut versuchen.' },
 });
 
+// H5: Register rate limit: 10 registrations per hour per IP (prevents account
+// flooding, audit-log spam, and bcrypt CPU abuse)
+const registerLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 10,
+  standardHeaders: true,
+  legacyHeaders: false,
+  message: { error: 'Zu viele Registrierungsversuche. Bitte später erneut versuchen.' },
+});
+
 // Punkt 23: Task creation rate limit: 20 per minute per user
 const taskCreateLimiter = rateLimit({
   windowMs: 60 * 1000,
@@ -43,4 +53,4 @@ const uploadLimiter = rateLimit({
   message: { error: 'Zu viele Upload-Anfragen. Bitte später erneut versuchen.' },
 });
 
-module.exports = { apiLimiter, loginLimiter, taskCreateLimiter, uploadLimiter };
\ No newline at end of file
+module.exports = { apiLimiter, loginLimiter, registerLimiter, taskCreateLimiter, uploadLimiter };
\ No newline at end of file
diff --git a/backend/middleware/validation.js b/backend/middleware/validation.js
index 76c4301..f556990 100644
--- a/backend/middleware/validation.js
+++ b/backend/middleware/validation.js
@@ -77,17 +77,35 @@ const updateTemplateSchema = z.object({
 });
 
 // ============ Task Schemas ============
+// H1: Whitelist für Datei-Pfade — nur Pfade akzeptieren, die exakt vom
+// Upload-Endpoint emittiert werden (/api/upload/uploads/<ts>-<rand>-<name>.<ext>).
+// Verhindert Stored XSS über javascript:/data:-URLs in Task-Dateilinks.
+// Endungen beschränkt auf die vom Uploader erlaubten Typen (inkl. .bin-Fallback
+// für abgelehnte Original-Endungen). Der Name-Teil ist bewusst `*` (nicht `+`),
+// da der Uploader auch Dateien mit leerem Basisnamen erzeugen kann (z.B. ".pdf").
+const UPLOAD_PATH_PATTERN = /^\/api\/upload\/uploads\/[0-9]+-[0-9]+-[a-zA-Z0-9._-]*\.(pdf|png|jpg|jpeg|gif|txt|doc|docx|bin)$/;
+const filePathSchema = z.string().regex(UPLOAD_PATH_PATTERN, 'Ungueltiger Dateipfad.');
+
+/**
+ * H1: Prüft, ob ein Pfad/URL ein legitimer Upload-Link ist.
+ * Wird auch in routes/tasks.js verwendet, um `value`-Felder von
+ * file_upload-Steps zu validieren (dort ist der Step-Typ erst serverseitig bekannt).
+ */
+function isSafeUploadPath(path) {
+  return typeof path === 'string' && UPLOAD_PATH_PATTERN.test(path);
+}
+
 const createTaskSchema = z.object({
   template_id: z.number().int().positive('Template-ID ist erforderlich.'),
   title: z.string().min(1, 'Titel ist erforderlich.').max(500),
   user_id: z.number().int().positive().optional(),
-  file_path: z.string().optional(),
+  file_path: filePathSchema.optional(),
   // V9: Limit task values array to prevent DoS via huge payloads
   values: z.array(z.object({
     step_id: z.number().int().positive().optional(),
     value: z.string().max(10000).optional(),
     is_checked: z.boolean().optional(),
-    file_path: z.string().optional(),
+    file_path: filePathSchema.optional(),
   })).max(100, 'Maximal 100 Werte pro Aufgabe erlaubt.').optional().default([]),
 });
 
@@ -206,4 +224,5 @@ module.exports = {
   // Middleware
   validate,
   validateQuery,
+  isSafeUploadPath,
 };
\ No newline at end of file
diff --git a/backend/migrations.js b/backend/migrations.js
index 4116f5f..787cffd 100644
--- a/backend/migrations.js
+++ b/backend/migrations.js
@@ -196,6 +196,28 @@ async function initDatabase() {
     }
   }, 60 * 60 * 1000);
 
+  // H4: uploads table — track file ownership for authorization on download
+  await migrate('add_uploads_table', isPostgres
+    ? `CREATE TABLE IF NOT EXISTS uploads (
+        id SERIAL PRIMARY KEY, filename TEXT UNIQUE NOT NULL, user_id INTEGER NOT NULL,
+        original_name TEXT, size INTEGER, created_at TIMESTAMP DEFAULT NOW(),
+        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+      )`
+    : `CREATE TABLE IF NOT EXISTS uploads (
+        id INTEGER PRIMARY KEY AUTOINCREMENT, filename TEXT UNIQUE NOT NULL, user_id INTEGER NOT NULL,
+        original_name TEXT, size INTEGER, created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+      )`
+  );
+  await migrate('idx_uploads_filename', isPostgres
+    ? `CREATE INDEX IF NOT EXISTS idx_uploads_filename ON uploads(filename)`
+    : `CREATE INDEX IF NOT EXISTS idx_uploads_filename ON uploads(filename)`
+  );
+  await migrate('idx_uploads_user_id', isPostgres
+    ? `CREATE INDEX IF NOT EXISTS idx_uploads_user_id ON uploads(user_id)`
+    : `CREATE INDEX IF NOT EXISTS idx_uploads_user_id ON uploads(user_id)`
+  );
+
   console.log('Datenbanktabellen initialisiert.');
 }
 
diff --git a/backend/routes/ad.js b/backend/routes/ad.js
index 51ed3d6..7636f94 100644
--- a/backend/routes/ad.js
+++ b/backend/routes/ad.js
@@ -84,9 +84,9 @@ router.post('/create-user', adminMiddleware, validate(createADUserSchema), async
 
     const result = await createADUser({ ou, vorname, nachname, email, username, password, department, telefon, titel, displayName, physicalDeliveryOfficeName, company, description, wWWHomePage, streetAddress, postOfficeBox, l, st, postalCode, c });
     if (result.warning && result.dn) {
-      auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `AD user created with warning: ${username} - ${result.warning}`);
+      auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `AD user created with warning: ${username} - ${result.warning}`, req);
     } else {
-      auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `Created AD user: ${username}`);
+      auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `Created AD user: ${username}`, req);
     }
 
     // Add user to groups if specified
@@ -95,7 +95,7 @@ router.post('/create-user', adminMiddleware, validate(createADUserSchema), async
       try {
         groupResults = await addUserToGroups(result.dn, groups);
         const addedCount = groupResults.filter(r => r.status === 'added').length;
-        auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `Added ${username} to ${addedCount} group(s)`);
+        auditLog(req.user?.id, 'ad.create-user', 'ad_user', null, `Added ${username} to ${addedCount} group(s)`, req);
       } catch (groupErr) {
         console.error('[WARN] Gruppenzuweisung fehlgeschlagen:', groupErr.message);
         groupResults = groups.map(dn => ({ dn, status: 'error', error: groupErr.message }));
@@ -104,7 +104,7 @@ router.post('/create-user', adminMiddleware, validate(createADUserSchema), async
 
     res.status(201).json({ ...result, groupResults });
   } catch (err) {
-    auditLog(req.user?.id, 'ad.create-user-failed', 'ad_user', null, `Failed to create AD user: ${username} - ${err.message}`);
+    auditLog(req.user?.id, 'ad.create-user-failed', 'ad_user', null, `Failed to create AD user: ${username} - ${err.message}`, req);
     res.status(500).json({ error: 'Interner Serverfehler.' });
   }
 });
@@ -114,7 +114,7 @@ router.delete('/delete-user', adminMiddleware, validate(deleteADUserSchema), asy
   const { dn } = req.validatedBody;
   try {
     await deleteADUser(dn);
-    auditLog(req.user?.id, 'ad.delete-user', 'ad_user', null, `Deleted AD user: ${dn}`);
+    auditLog(req.user?.id, 'ad.delete-user', 'ad_user', null, `Deleted AD user: ${dn}`, req);
     res.json({ success: true, message: 'Benutzer erfolgreich gelöscht.' });
   } catch (err) {
     res.status(500).json({ error: 'Fehler beim Löschen des AD-Benutzers: ' + err.message });
diff --git a/backend/routes/auth.js b/backend/routes/auth.js
index fa8ff62..e768722 100644
--- a/backend/routes/auth.js
+++ b/backend/routes/auth.js
@@ -11,20 +11,20 @@ const db = require('../db');
 const { auditLog } = require('../auditLog');
 const { authMiddleware, adminMiddleware, createSession, deleteSession, invalidateUserSessions, isAccountLocked, recordFailedLogin, recordSuccessfulLogin, setAuthCookie, clearAuthCookie, setCSRFCookie, hashToken } = require('../middleware/auth');
 const { isLDAPConfigured, authenticateLDAP } = require('../ldapSync');
-const { loginLimiter } = require('../middleware/rateLimit');
+const { loginLimiter, registerLimiter } = require('../middleware/rateLimit');
 const { validate, registerSchema, loginSchema } = require('../middleware/validation');
 
 const router = express.Router();
 
 // Register
-router.post('/register', validate(registerSchema), async (req, res) => {
+router.post('/register', registerLimiter, validate(registerSchema), async (req, res) => {
   const { email, password, name } = req.validatedBody;
   try {
     const hash = bcrypt.hashSync(password, 10);
     // VULN-FIX: Force role to 'user' - never trust client-supplied role on register
     const info = await db.prepare('INSERT INTO users (email, password, name, role, status, source) VALUES (?, ?, ?, \'user\', \'inaktiv\', \'local\')').run(email, hash, name);
     const userId = info.lastInsertRowid;
-    auditLog(null, 'register', 'user', userId, `New registration: ${email}`);
+    auditLog(null, 'register', 'user', userId, `New registration: ${email}`, req);
     // P4: Set CSRF cookie for the new session
     const csrfToken = setCSRFCookie(res);
     // Return correct status 'inaktiv' (Punkt 5 fix)
@@ -54,8 +54,9 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
       try {
         const ldapResult = await authenticateLDAP(email, password);
         const adRow = await db.prepare('SELECT id, email, name, role, status, source, username FROM users WHERE LOWER(username) = LOWER(?)').get(ldapResult.username);
-        if (!adRow) return res.status(404).json({ error: 'Nutzer im System nicht gefunden. Bitte warte auf die naechste Synchronisation.' });
-        if (adRow.status === 'inaktiv') return res.status(403).json({ error: 'Dein Konto ist deaktiviert.' });
+        // M3: Unified error messages — don't reveal whether the account exists
+        if (!adRow) return res.status(401).json({ error: 'Ungueltige Anmeldedaten.' });
+        if (adRow.status === 'inaktiv') return res.status(401).json({ error: 'Ungueltige Anmeldedaten.' });
         await recordSuccessfulLogin(adRow.id);
         // V6: Pass old token for session rotation (prevents session fixation)
         const oldToken = req.cookies?.workflow_token || req.headers.authorization?.replace('Bearer ', '');
@@ -63,7 +64,7 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
         setAuthCookie(res, rawToken); // Punkt 8: HttpOnly-Cookie
         // P4: CSRF cookie derived from the new session token (deterministic, self-healing)
         const csrfToken = setCSRFCookie(res, hashToken(rawToken));
-        auditLog(adRow.id, 'login', 'user', adRow.id, 'AD login');
+        auditLog(adRow.id, 'login', 'user', adRow.id, 'AD login', req);
         // Bug 6: Don't expose token in response body (cookie-only auth)
         res.json({ ...adRow, csrfToken });
       } catch (ldapErr) {
@@ -76,12 +77,14 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
   }
 
   if (row.status === 'inaktiv') {
-    return res.status(403).json({ error: 'Dein Konto ist deaktiviert. Bitte wende dich an einen Administrator.' });
+    // M3: Unified error message — don't reveal whether the account exists
+    return res.status(401).json({ error: 'Ungueltige Anmeldedaten.' });
   }
 
   if (row.source === 'ad') {
     if (!isLDAPConfigured()) {
-      return res.status(403).json({ error: 'AD-Anmeldung nicht konfiguriert.' });
+      // M3: Unified error message
+      return res.status(401).json({ error: 'Ungueltige Anmeldedaten.' });
     }
     try {
       await authenticateLDAP(row.username || row.email.split('@')[0], password);
@@ -92,7 +95,7 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
       setAuthCookie(res, rawToken); // Punkt 8: HttpOnly-Cookie
       // P4: CSRF cookie derived from the new session token (deterministic, self-healing)
       const csrfToken = setCSRFCookie(res, hashToken(rawToken));
-      auditLog(row.id, 'login', 'user', row.id, 'AD login');
+      auditLog(row.id, 'login', 'user', row.id, 'AD login', req);
       const { password: _, ...safeRow } = row;
       // Bug 6: Don't expose token in response body (cookie-only auth)
       res.json({ ...safeRow, csrfToken });
@@ -110,7 +113,7 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
       passwordMatch = row.password === password;
       if (passwordMatch) {
         // P8: Log plaintext login for security monitoring (auto-upgrade follows)
-        auditLog(row.id, 'plaintext_login_upgraded', 'user', row.id, 'Legacy plaintext password upgraded to bcrypt');
+        auditLog(row.id, 'plaintext_login_upgraded', 'user', row.id, 'Legacy plaintext password upgraded to bcrypt', req);
         console.warn('[SECURITY] User', row.email, 'logged in with plaintext password - upgrading to bcrypt.');
         const hash = bcrypt.hashSync(password, 12); // Punkt 10: 12 rounds per OWASP
         await db.prepare('UPDATE users SET password = ? WHERE id = ?').run(hash, row.id);
@@ -127,7 +130,7 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
     setAuthCookie(res, rawToken); // Punkt 8: HttpOnly-Cookie
     // P4: CSRF cookie derived from the new session token (deterministic, self-healing)
     const csrfToken = setCSRFCookie(res, hashToken(rawToken));
-    auditLog(row.id, 'login', 'user', row.id, 'Local login');
+    auditLog(row.id, 'login', 'user', row.id, 'Local login', req);
     const { password: _, ...safeRow } = row;
     // Bug 6: Don't expose token in response body (cookie-only auth)
     res.json({ ...safeRow, csrfToken });
@@ -137,7 +140,7 @@ router.post('/login', loginLimiter, validate(loginSchema), async (req, res) => {
 // Logout
 router.post('/logout', async (req, res) => {
   const rawToken = req.cookies?.workflow_token || req.headers.authorization?.replace('Bearer ', '');
-  await deleteSession(rawToken);
+  await deleteSession(rawToken, req);
   clearAuthCookie(res); // Punkt 8: Clear HttpOnly-Cookie
   res.json({ message: 'Abgemeldet.' });
 });
diff --git a/backend/routes/stats.js b/backend/routes/stats.js
index 3dfc607..6b2688e 100644
--- a/backend/routes/stats.js
+++ b/backend/routes/stats.js
@@ -49,8 +49,11 @@ router.get('/stats', async (req, res) => {
       stats[newKey] = typeof value === 'string' ? Number(value) : value;
     }
 
+    // Top 5 Vorlagen nach Task-Anzahl (Graph zeigt max. 5 Säulen).
+    // HAVING filtert Vorlagen ohne Tasks heraus, damit der Graph nur
+    // tatsächlich genutzte Vorlagen zeigt.
     const topTemplates = await db.prepare(
-      'SELECT t.id, t.name, COUNT(tk.id) as task_count FROM templates t LEFT JOIN tasks tk ON t.id = tk.template_id GROUP BY t.id ORDER BY task_count DESC LIMIT 5'
+      'SELECT t.id, t.name, COUNT(tk.id) as task_count FROM templates t LEFT JOIN tasks tk ON t.id = tk.template_id GROUP BY t.id HAVING COUNT(tk.id) > 0 ORDER BY task_count DESC LIMIT 5'
     ).all();
 
     const recentActivity = await db.prepare(
diff --git a/backend/routes/tasks.js b/backend/routes/tasks.js
index 0325e53..a87e967 100644
--- a/backend/routes/tasks.js
+++ b/backend/routes/tasks.js
@@ -10,12 +10,60 @@ const db = require('../db');
 const { auditLog } = require('../auditLog');
 const { authMiddleware, adminMiddleware } = require('../middleware/auth');
 const { taskCreateLimiter } = require('../middleware/rateLimit');
-const { validate, validateQuery, createTaskSchema, updateTaskStatusSchema, updateTaskValuesSchema, addTaskFieldSchema, paginationSchema } = require('../middleware/validation');
+const { validate, validateQuery, createTaskSchema, updateTaskStatusSchema, updateTaskValuesSchema, addTaskFieldSchema, paginationSchema, isSafeUploadPath } = require('../middleware/validation');
 
 const router = express.Router();
 
 router.use(authMiddleware);
 
+// H1: Defense-in-Depth — file_upload-Step-Werte werden als Download-Link
+// gerendert. Nur Pfade akzeptieren, die exakt vom Upload-Endpoint stammen,
+// damit kein javascript:/data:-XSS über den Wert eingeschleust werden kann.
+// (Der Step-Typ ist erst serverseitig bekannt, daher die Prüfung hier.)
+// Variante für Task-Create: Werte tragen step_id, Step-Typ wird nachgeschlagen.
+async function validateFileUploadValues(values) {
+  const stepIds = values.map(v => v.step_id).filter(id => Number.isInteger(id));
+  if (stepIds.length === 0) return;
+  const placeholders = stepIds.map(() => '?').join(',');
+  const steps = await db.prepare(`SELECT id, type FROM template_steps WHERE id IN (${placeholders})`).all(...stepIds);
+  const typeMap = {};
+  steps.forEach(s => { typeMap[s.id] = s.type; });
+  for (const v of values) {
+    if (v.step_id && typeMap[v.step_id] === 'file_upload' && v.value && !isSafeUploadPath(v.value)) {
+      const err = new Error('Ungueltiger Dateipfad in Werten.');
+      err.status = 400;
+      throw err;
+    }
+  }
+}
+
+// H1: Variante für Task-Values-Update (PUT /:id/values): Das Schema enthält
+// kein step_id, daher wird der Step-Typ über die bestehenden task_values
+// ermittelt. Werte, die unverändert zum DB-Stand sind, werden akzeptiert
+// (Legacy-Daten blockieren keine legitimen Edits); nur NEU gesetzte unsichere
+// Werte werden abgelehnt.
+async function validateFileUploadValueUpdates(taskId, values) {
+  const ids = values.map(v => v.id).filter(id => Number.isInteger(id));
+  if (ids.length === 0) return;
+  const placeholders = ids.map(() => '?').join(',');
+  const rows = await db.prepare(
+    `SELECT tv.id, tv.value as old_value, ts.type as step_type
+     FROM task_values tv LEFT JOIN template_steps ts ON tv.step_id = ts.id
+     WHERE tv.task_id = ? AND tv.id IN (${placeholders})`
+  ).all(taskId, ...ids);
+  const rowMap = {};
+  rows.forEach(r => { rowMap[r.id] = r; });
+  for (const v of values) {
+    const row = rowMap[v.id];
+    if (!row) continue; // Fremde/unbekannte IDs scheitern später am UPDATE selbst
+    if (row.step_type === 'file_upload' && v.value && v.value !== row.old_value && !isSafeUploadPath(v.value)) {
+      const err = new Error('Ungueltiger Dateipfad in Werten.');
+      err.status = 400;
+      throw err;
+    }
+  }
+}
+
 // Create task - Punkt 8: Transaction
 router.post('/', taskCreateLimiter, validate(createTaskSchema), async (req, res) => {
   const { template_id, title, values, file_path, user_id } = req.validatedBody;
@@ -27,22 +75,33 @@ router.post('/', taskCreateLimiter, validate(createTaskSchema), async (req, res)
     return res.status(400).json({ error: 'template_id und title sind erforderlich.' });
   }
 
-  const insertTask = db.prepare('INSERT INTO tasks (template_id, user_id, title, status, file_path) VALUES (?, ?, ?, \'offen\', ?)');
-  const insertValue = db.prepare('INSERT INTO task_values (task_id, step_id, value, is_checked, file_path, snap_label, snap_type, snap_page_num, snap_ad_field, snap_ad_prefix, snap_dropdown_options, snap_email_source_fields, snap_hidden) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
+  // H1: file_upload-Step-Werte gegen Upload-Whitelist prüfen (XSS-Schutz)
+  try {
+    await validateFileUploadValues(values);
+  } catch (err) {
+    return res.status(err.status || 400).json({ error: err.message });
+  }
+
+  // H2: Alle Statements innerhalb der Transaktion MÜSSEN über txDb.prepare()
+  // erzeugt werden (fn erhält txDb als this) — sonst laufen sie außerhalb der
+  // Transaktion und ein Rollback ist unmöglich.
+  const createTask = db.transaction(async function () {
+    const txDb = this;
+    const insertTask = txDb.prepare('INSERT INTO tasks (template_id, user_id, title, status, file_path) VALUES (?, ?, ?, \'offen\', ?)');
+    const insertValue = txDb.prepare('INSERT INTO task_values (task_id, step_id, value, is_checked, file_path, snap_label, snap_type, snap_page_num, snap_ad_field, snap_ad_prefix, snap_dropdown_options, snap_email_source_fields, snap_hidden) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
 
-  const createTask = db.transaction(async () => {
     const info = await insertTask.run(template_id, targetUserId, title, file_path);
     const taskId = info.lastInsertRowid;
 
     if (values.length > 0) {
-      // Fetch step metadata for snapshot
+      // Fetch step metadata for snapshot (auch über txDb — konsistente Connection)
       const stepIds = values.map(v => v.step_id).filter(Boolean);
       const stepMetaMap = {};
       if (stepIds.length > 0) {
         const validStepIds = stepIds.filter(id => Number.isInteger(id));
         if (validStepIds.length > 0) {
           const placeholders = validStepIds.map(() => '?').join(',');
-          const steps = await db.prepare(`SELECT id, label, type, page_num, ad_field, ad_prefix, dropdown_options, email_source_fields, hidden FROM template_steps WHERE id IN (${placeholders})`).all(...validStepIds);
+          const steps = await txDb.prepare(`SELECT id, label, type, page_num, ad_field, ad_prefix, dropdown_options, email_source_fields, hidden FROM template_steps WHERE id IN (${placeholders})`).all(...validStepIds);
           steps.forEach(s => { stepMetaMap[s.id] = s; });
         }
       }
@@ -67,7 +126,7 @@ router.post('/', taskCreateLimiter, validate(createTaskSchema), async (req, res)
 
   try {
     const taskId = await createTask();
-    auditLog(req.user?.id, 'create_task', 'task', taskId, `Task created: ${title}`);
+    auditLog(req.user?.id, 'create_task', 'task', taskId, `Task created: ${title}`, req);
     res.status(201).json({ id: taskId, template_id, user_id: targetUserId, title, status: 'offen', file_path, values });
   } catch (err) {
     console.error('[ERROR] POST /tasks -', err.message);
@@ -87,7 +146,7 @@ router.patch('/:id/status', validate(updateTaskStatusSchema), async (req, res) =
   }
   const info = await db.prepare('UPDATE tasks SET status = ? WHERE id = ?').run(status, taskId);
   if (info.changes === 0) return res.status(404).json({ error: 'Aufgabe nicht gefunden.' });
-  auditLog(req.user?.id, 'update_task', 'task', taskId, `Status changed to: ${status}`);
+  auditLog(req.user?.id, 'update_task', 'task', taskId, `Status changed to: ${status}`, req);
   res.json({ id: taskId, status });
 });
 
@@ -96,8 +155,17 @@ router.put('/:id/values', adminMiddleware, validate(updateTaskValuesSchema), asy
   const taskId = parseInt(req.params.id);
   const { values } = req.validatedBody;
 
-  const updateValue = db.prepare('UPDATE task_values SET value = ?, is_checked = ? WHERE id = ? AND task_id = ?');
-  const updateTransaction = db.transaction(async (vals) => {
+  // H1: Auch beim Admin-Update nur sichere Upload-Pfade für file_upload-Steps akzeptieren
+  try {
+    await validateFileUploadValueUpdates(taskId, values);
+  } catch (err) {
+    return res.status(err.status || 400).json({ error: err.message });
+  }
+
+  // H2: Statements innerhalb der Transaktion über txDb erzeugen
+  const updateTransaction = db.transaction(async function (vals) {
+    const txDb = this;
+    const updateValue = txDb.prepare('UPDATE task_values SET value = ?, is_checked = ? WHERE id = ? AND task_id = ?');
     let updated = 0;
     for (const v of vals) {
       const info = await updateValue.run(v.value || '', v.is_checked ? 1 : 0, v.id, taskId);
@@ -108,7 +176,7 @@ router.put('/:id/values', adminMiddleware, validate(updateTaskValuesSchema), asy
 
   try {
     const updated = await updateTransaction(values);
-    auditLog(req.user?.id, 'update_task', 'task', taskId, `Updated ${updated} task values`);
+    auditLog(req.user?.id, 'update_task', 'task', taskId, `Updated ${updated} task values`, req);
     res.json({ updated, taskId });
   } catch (err) {
     res.status(500).json({ error: 'Interner Serverfehler.' });
@@ -131,7 +199,7 @@ router.post('/:id/add-field', adminMiddleware, validate(addTaskFieldSchema), asy
       'INSERT INTO task_values (task_id, step_id, value, is_checked, custom_label, custom_type, custom_dropdown_options, custom_ad_field, custom_hidden, custom_email_source_fields) VALUES (?, NULL, ?, ?, ?, ?, ?, ?, ?, ?)'
     ).run(taskId, fieldValue, fieldType === 'checkbox' ? 0 : 0, label.trim(), fieldType, customDropdownOptions, customAdField, customHidden, customEmailSourceFields);
 
-    auditLog(req.user?.id, 'task.add-field', 'task', taskId, `Added field: ${label.trim()}`);
+    auditLog(req.user?.id, 'task.add-field', 'task', taskId, `Added field: ${label.trim()}`, req);
     res.status(201).json({
       id: info.lastInsertRowid, task_id: taskId, custom_label: label.trim(), custom_type: fieldType,
       value: fieldValue, page_num: page_num || 1,
@@ -150,7 +218,7 @@ router.delete('/:id/fields/:fieldId', adminMiddleware, async (req, res) => {
   const fieldId = parseInt(req.params.fieldId);
   const info = await db.prepare('DELETE FROM task_values WHERE id = ? AND task_id = ? AND custom_label IS NOT NULL').run(fieldId, taskId);
   if (info.changes === 0) return res.status(404).json({ error: 'Feld nicht gefunden oder kein benutzerdefiniertes Feld.' });
-  auditLog(req.user?.id, 'task.delete-field', 'task', taskId, `Deleted field: ${fieldId}`);
+  auditLog(req.user?.id, 'task.delete-field', 'task', taskId, `Deleted field: ${fieldId}`, req);
   res.json({ message: 'Feld gelöscht.' });
 });
 
@@ -159,7 +227,7 @@ router.delete('/:id', adminMiddleware, async (req, res) => {
   const taskId = parseInt(req.params.id);
   const info = await db.prepare('DELETE FROM tasks WHERE id = ?').run(taskId);
   if (info.changes === 0) return res.status(404).json({ error: 'Aufgabe nicht gefunden.' });
-  auditLog(req.user?.id, 'delete_task', 'task', taskId, null);
+  auditLog(req.user?.id, 'delete_task', 'task', taskId, null, req);
   res.json({ message: 'Aufgabe gelöscht.' });
 });
 
@@ -169,11 +237,16 @@ router.get('/:id', async (req, res) => {
   const task = await db.prepare('SELECT t.*, u.name as user_name, u.email as user_email, tpl.name as template_name, tpl.ad_create FROM tasks t LEFT JOIN users u ON t.user_id = u.id LEFT JOIN templates tpl ON t.template_id = tpl.id WHERE t.id = ?').get(taskId);
   if (!task) return res.status(404).json({ error: 'Aufgabe nicht gefunden.' });
 
+  // K2: BOLA protection — non-admins may only read their own tasks
+  if (task.user_id !== req.user.id && req.user.role !== 'admin') {
+    return res.status(403).json({ error: 'Keine Berechtigung, diese Aufgabe anzuzeigen.' });
+  }
+
   const values = await db.prepare(
     `SELECT tv.*, COALESCE(ts.label, tv.snap_label) as step_label, COALESCE(ts.type, tv.snap_type) as step_type, COALESCE(ts.page_num, tv.snap_page_num) as page_num, COALESCE(ts.ad_field, tv.snap_ad_field) as ad_field, COALESCE(ts.ad_prefix, tv.snap_ad_prefix) as ad_prefix, COALESCE(ts.dropdown_options, tv.snap_dropdown_options) as dropdown_options, COALESCE(ts.email_source_fields, tv.snap_email_source_fields) as email_source_fields, COALESCE(ts.hidden, tv.snap_hidden) as hidden, tv.custom_label, tv.custom_type, tv.custom_dropdown_options, tv.custom_ad_field, tv.custom_hidden, tv.custom_email_source_fields FROM task_values tv LEFT JOIN template_steps ts ON tv.step_id = ts.id WHERE tv.task_id = ? ORDER BY ts.step_order ASC, tv.id ASC`
   ).all(taskId);
 
-  auditLog(req.user?.id, 'view_task', 'task', taskId, null);
+  auditLog(req.user?.id, 'view_task', 'task', taskId, null, req);
   res.json({ ...task, values: values || [] });
 });
 
@@ -183,10 +256,14 @@ router.get('/', validateQuery(paginationSchema), async (req, res) => {
   const offset = (page - 1) * limit;
   const status = req.query.status;
 
-  let whereClause = '';
+  // K2: BOLA protection — non-admins only see their own tasks
+  const isAdmin = req.user.role === 'admin';
+  let whereClause = isAdmin ? '' : ' WHERE t.user_id = ?';
   const params = [];
+  if (!isAdmin) params.push(req.user.id);
+
   if (status && ['offen', 'erledigt'].includes(status)) {
-    whereClause = ' WHERE t.status = ?';
+    whereClause = isAdmin ? ' WHERE t.status = ?' : ' AND t.status = ?';
     params.push(status);
   }
 
diff --git a/backend/routes/templates.js b/backend/routes/templates.js
index 9367dc7..36ddb53 100644
--- a/backend/routes/templates.js
+++ b/backend/routes/templates.js
@@ -39,11 +39,13 @@ router.post('/', adminMiddleware, validate(createTemplateSchema), async (req, re
   const fileUpload = allows_file_upload ? 1 : 0;
   const adCreate = ad_create ? 1 : 0;
 
-  const insertTemplate = db.prepare('INSERT INTO templates (name, description, is_assignable, allows_file_upload, ad_create) VALUES (?, ?, ?, ?, ?)');
-  const insertStep = db.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
+  // H2: Alle Statements innerhalb der Transaktion über txDb erzeugen
+  // (fn erhält txDb als this) — sonst kein Rollback möglich.
+  const createTemplate = db.transaction(async function () {
+    const txDb = this;
+    const insertTemplate = txDb.prepare('INSERT INTO templates (name, description, is_assignable, allows_file_upload, ad_create) VALUES (?, ?, ?, ?, ?)');
+    const insertStep = txDb.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
 
-  // Punkt 8: Transaction for template + steps
-  const createTemplate = db.transaction(async () => {
     const info = await insertTemplate.run(name, description, assignable, fileUpload, adCreate);
     const templateId = info.lastInsertRowid;
 
@@ -60,7 +62,7 @@ router.post('/', adminMiddleware, validate(createTemplateSchema), async (req, re
 
   try {
     const templateId = await createTemplate();
-    auditLog(req.user?.id, 'create_template', 'template', templateId, `Created template: ${name}`);
+    auditLog(req.user?.id, 'create_template', 'template', templateId, `Created template: ${name}`, req);
     res.status(201).json({ id: templateId, name, description, is_assignable: !!assignable, allows_file_upload: !!fileUpload, ad_create: !!adCreate, steps });
   } catch (err) {
     res.status(500).json({ error: 'Interner Serverfehler.' });
@@ -76,12 +78,13 @@ router.put('/:id', adminMiddleware, validate(updateTemplateSchema), async (req,
   const fileUpload = allows_file_upload ? 1 : 0;
   const adCreate = ad_create ? 1 : 0;
 
-  const updateTemplate = db.prepare('UPDATE templates SET name = ?, description = ?, is_assignable = ?, allows_file_upload = ?, ad_create = ? WHERE id = ?');
-  const deleteSteps = db.prepare('DELETE FROM template_steps WHERE template_id = ?');
-  const insertStep = db.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
+  // H2: Statements innerhalb der Transaktion über txDb erzeugen
+  const updateTemplateTransaction = db.transaction(async function () {
+    const txDb = this;
+    const updateTemplate = txDb.prepare('UPDATE templates SET name = ?, description = ?, is_assignable = ?, allows_file_upload = ?, ad_create = ? WHERE id = ?');
+    const deleteSteps = txDb.prepare('DELETE FROM template_steps WHERE template_id = ?');
+    const insertStep = txDb.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');
 
-  // Punkt 8: Transaction for update + delete old steps + insert new steps
-  const updateTemplateTransaction = db.transaction(async () => {
     const info = await updateTemplate.run(name, description, assignable, fileUpload, adCreate, templateId);
     if (info.changes === 0) throw new Error('NOT_FOUND');
 
@@ -99,7 +102,7 @@ router.put('/:id', adminMiddleware, validate(updateTemplateSchema), async (req,
 
   try {
     await updateTemplateTransaction();
-    auditLog(req.user?.id, 'update_template', 'template', templateId, `Updated template: ${name}`);
+    auditLog(req.user?.id, 'update_template', 'template', templateId, `Updated template: ${name}`, req);
     res.json({ id: templateId, name, description, is_assignable: !!assignable, allows_file_upload: !!fileUpload, ad_create: !!adCreate, steps });
   } catch (err) {
     if (err.message === 'NOT_FOUND') return res.status(404).json({ error: 'Vorlage nicht gefunden.' });
@@ -112,7 +115,7 @@ router.delete('/:id', adminMiddleware, async (req, res) => {
   const templateId = parseInt(req.params.id);
   const info = await db.prepare('DELETE FROM templates WHERE id = ?').run(templateId);
   if (info.changes === 0) return res.status(404).json({ error: 'Vorlage nicht gefunden.' });
-  auditLog(req.user?.id, 'delete_template', 'template', templateId, null);
+  auditLog(req.user?.id, 'delete_template', 'template', templateId, null, req);
   res.json({ message: 'Vorlage gelöscht.' });
 });
 
diff --git a/backend/routes/upload.js b/backend/routes/upload.js
index 5a861cc..1baa2ba 100644
--- a/backend/routes/upload.js
+++ b/backend/routes/upload.js
@@ -1,13 +1,18 @@
 /**
  * File upload routes module.
+ *
+ * H4: Download authorization — files are tracked in the `uploads` table with
+ * owner_id. A user may download a file only if they own it or are admin.
+ * Legacy files (not in the table) are admin-only by default.
  */
 const express = require('express');
 const path = require('path');
 const fs = require('fs');
 const multer = require('multer');
-const { authMiddleware } = require('../middleware/auth');
+const { authMiddleware, adminMiddleware } = require('../middleware/auth');
 const { uploadLimiter } = require('../middleware/rateLimit');
 const { auditLog } = require('../auditLog');
+const db = require('../db');
 
 const router = express.Router();
 
@@ -21,6 +26,25 @@ if (!fs.existsSync(uploadDir)) {
 const ALLOWED_MIMES = ['application/pdf', 'image/png', 'image/jpeg', 'image/gif', 'text/plain', 'application/msword', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document'];
 const ALLOWED_EXTS = ['.pdf', '.png', '.jpg', '.jpeg', '.gif', '.txt', '.doc', '.docx'];
 
+// H4: Magic-byte signatures for the most common allowed types. We verify the
+// first bytes of the uploaded file to reject MIME-spoofed payloads.
+const MAGIC_BYTES = [
+  { ext: '.pdf', mime: 'application/pdf', bytes: [0x25, 0x50, 0x44, 0x46] }, // %PDF
+  { ext: '.png', mime: 'image/png', bytes: [0x89, 0x50, 0x4E, 0x47] }, // PNG
+  { ext: '.jpg', mime: 'image/jpeg', bytes: [0xFF, 0xD8, 0xFF] },
+  { ext: '.jpeg', mime: 'image/jpeg', bytes: [0xFF, 0xD8, 0xFF] },
+  { ext: '.gif', mime: 'image/gif', bytes: [0x47, 0x49, 0x46, 0x38] }, // GIF8
+];
+
+function detectMagic(buf) {
+  for (const sig of MAGIC_BYTES) {
+    if (buf.length >= sig.bytes.length && sig.bytes.every((b, i) => buf[i] === b)) {
+      return sig;
+    }
+  }
+  return null;
+}
+
 const storage = multer.diskStorage({
   destination: (req, file, cb) => cb(null, uploadDir),
   filename: (req, file, cb) => {
@@ -44,22 +68,69 @@ const upload = multer({
   },
 });
 
-// P12: Serve uploads as attachments (prevent XSS) - requires authentication
-router.use('/uploads', authMiddleware, express.static(uploadDir, {
-  setHeaders: (res) => {
-    res.setHeader('Content-Disposition', 'attachment');
-    res.setHeader('X-Content-Type-Options', 'nosniff');
-  },
-}));
+// H4: Authorized download — replaces the previous static serving which let any
+// logged-in user download any file. Ownership is verified against the uploads
+// table; legacy files (not tracked) are admin-only.
+router.get('/uploads/:filename', authMiddleware, async (req, res) => {
+  const filename = path.basename(req.params.filename);
+  // Block path traversal — only allow safe characters that the uploader itself emits
+  if (!/^[0-9]+-[0-9]+-[a-zA-Z0-9._-]+\.[a-zA-Z0-9]+$/.test(filename)) {
+    return res.status(400).json({ error: 'Ungültiger Dateiname.' });
+  }
+
+  const filePath = path.join(uploadDir, filename);
+  if (!fs.existsSync(filePath)) {
+    return res.status(404).json({ error: 'Datei nicht gefunden.' });
+  }
+
+  const uploadRow = await db.prepare('SELECT user_id FROM uploads WHERE filename = ?').get(filename);
+  const isAdmin = req.user.role === 'admin';
+  if (uploadRow) {
+    if (uploadRow.user_id !== req.user.id && !isAdmin) {
+      return res.status(403).json({ error: 'Keine Berechtigung, diese Datei herunterzuladen.' });
+    }
+  } else if (!isAdmin) {
+    // Legacy file not tracked in uploads table — admin only
+    return res.status(403).json({ error: 'Keine Berechtigung, diese Datei herunterzuladen.' });
+  }
+
+  res.setHeader('Content-Disposition', 'attachment');
+  res.setHeader('X-Content-Type-Options', 'nosniff');
+  res.sendFile(filePath);
+});
 
 // Upload endpoint - Punkt 23: Rate limited per user
-router.post('/', authMiddleware, uploadLimiter, upload.single('file'), (req, res) => {
+router.post('/', authMiddleware, uploadLimiter, upload.single('file'), async (req, res) => {
   if (!req.file) {
     return res.status(400).json({ error: 'Keine Datei hochgeladen.' });
   }
-  const fileUrl = '/uploads/' + req.file.filename;
-  auditLog(req.user?.id, 'file_upload', null, null, `Uploaded: ${req.file.filename} (${req.file.size} bytes)`);
+
+  // H4: Magic-byte verification — reject files whose content doesn't match
+  // the declared type (MIME spoofing). Text/Office types have no stable magic
+  // bytes, so we only enforce the binary types we can verify.
+  const buf = fs.readFileSync(req.file.path, { encoding: null, flag: 'r' });
+  const detected = detectMagic(buf);
+  const declaredExt = path.extname(req.file.filename).toLowerCase();
+  if (detected && detected.ext !== declaredExt) {
+    // Content doesn't match extension — delete and reject
+    fs.unlink(req.file.path, () => {});
+    auditLog(req.user?.id, 'file_upload_rejected', null, null, `Magic-byte mismatch: ${req.file.filename} (declared ${declaredExt}, detected ${detected.ext})`, req);
+    return res.status(400).json({ error: 'Dateiinhalt passt nicht zur Dateiendung.' });
+  }
+
+  // H4: Record ownership so download authorization can be enforced
+  try {
+    await db.prepare('INSERT INTO uploads (filename, user_id, original_name, size) VALUES (?, ?, ?, ?)')
+      .run(req.file.filename, req.user.id, req.file.originalname, req.file.size);
+  } catch (err) {
+    // If the uploads table isn't created yet (migration not applied), we still
+    // allow the upload but log the error — the file itself is already on disk.
+    console.error('[UPLOAD] uploads-Tabelle nicht verfügbar:', err.message);
+  }
+
+  const fileUrl = '/api/upload/uploads/' + req.file.filename;
+  auditLog(req.user?.id, 'file_upload', null, null, `Uploaded: ${req.file.filename} (${req.file.size} bytes)`, req);
   res.json({ filename: req.file.filename, originalname: req.file.originalname, url: fileUrl, size: req.file.size });
 });
 
-module.exports = router;
\ No newline at end of file
+module.exports = router;
diff --git a/backend/routes/users.js b/backend/routes/users.js
index 522fd0b..1e60336 100644
--- a/backend/routes/users.js
+++ b/backend/routes/users.js
@@ -49,7 +49,7 @@ router.post('/', adminMiddleware, validate(createUserSchema), async (req, res) =
   try {
     const hash = bcrypt.hashSync(password, 12); // Punkt 10: 12 rounds per OWASP
     const info = await db.prepare('INSERT INTO users (email, password, name, role, status, source) VALUES (?, ?, ?, ?, ?, \'local\')').run(email, hash, name, role, status);
-    auditLog(req.user?.id, 'create_user', 'user', info.lastInsertRowid, `Created user: ${email}`);
+    auditLog(req.user?.id, 'create_user', 'user', info.lastInsertRowid, `Created user: ${email}`, req);
     res.status(201).json({ id: info.lastInsertRowid, email, name, role, status, source: 'local' });
   } catch (err) {
     if (err.message && err.message.includes('UNIQUE constraint')) {
@@ -62,7 +62,6 @@ router.post('/', adminMiddleware, validate(createUserSchema), async (req, res) =
 // Update user
 router.put('/:id', validate(updateUserSchema), async (req, res) => {
   const userId = parseInt(req.params.id);
-  const { email, name, password, role, status, current_password } = req.validatedBody;
 
   // VULN-04: Authorization check - only admin or self (with restrictions)
   const isSelf = req.user.id === userId;
@@ -70,12 +69,18 @@ router.put('/:id', validate(updateUserSchema), async (req, res) => {
   if (!isAdmin && !isSelf) {
     return res.status(403).json({ error: 'Keine Berechtigung, diesen Nutzer zu bearbeiten.' });
   }
-  // Non-admins may NOT change role or status (privilege escalation prevention)
+
+  // K1: Strip role/status FIRST for non-admins (BEFORE reading values) to prevent
+  // privilege escalation via mass assignment. Earlier code destructured first
+  // and deleted afterwards, which left the local copies intact.
   if (!isAdmin) {
     delete req.validatedBody.role;
     delete req.validatedBody.status;
   }
 
+  // Now safe to read — non-admins can never see role/status here
+  const { email, name, password, role, status, current_password } = req.validatedBody;
+
   // P7: Non-admins changing their own password must verify the current password
   if (!isAdmin && isSelf && password && password.trim()) {
     if (!current_password) {
@@ -108,7 +113,7 @@ router.put('/:id', validate(updateUserSchema), async (req, res) => {
       return res.status(400).json({ error: 'Status muss "aktiv" oder "inaktiv" sein.' });
     }
     await db.prepare('UPDATE users SET role = ?, status = ? WHERE id = ?').run(finalRole, finalStatus, userId);
-    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated AD user role/status`);
+    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated AD user role/status`, req);
     return res.json({ id: userId, email: user.email, name: user.name, role: finalRole, status: finalStatus, source: user.source, username: user.username });
   }
 
@@ -139,7 +144,7 @@ router.put('/:id', validate(updateUserSchema), async (req, res) => {
     }
     // VULN-13: Invalidate all sessions for this user after password change
     await invalidateUserSessions(userId);
-    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user with new password (sessions invalidated)`);
+    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user with new password (sessions invalidated)`, req);
     res.json({ id: userId, email, name: finalName, role: finalRole, status: finalStatus, source: user.source, username: user.username });
   } else {
     try {
@@ -150,7 +155,7 @@ router.put('/:id', validate(updateUserSchema), async (req, res) => {
       }
       throw err;
     }
-    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user`);
+    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user`, req);
     res.json({ id: userId, email, name: finalName, role: finalRole, status: finalStatus, source: user.source, username: user.username });
   }
 });
@@ -165,7 +170,7 @@ router.delete('/:id', adminMiddleware, async (req, res) => {
   }
   const info = await db.prepare('DELETE FROM users WHERE id = ?').run(userId);
   if (info.changes === 0) return res.status(404).json({ error: 'Nutzer nicht gefunden.' });
-  auditLog(req.user?.id, 'delete_user', 'user', userId, `Deleted user: ${user.email}`);
+  auditLog(req.user?.id, 'delete_user', 'user', userId, `Deleted user: ${user.email}`, req);
   res.json({ message: 'Nutzer geloescht.' });
 });
 
diff --git a/backend/server.js b/backend/server.js
index d3d62b7..4919943 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -60,6 +60,15 @@ const validCorsOrigins = rawCorsOrigin
   .filter(o => o && /^https?:\/\/.+/.test(o));
 const cspConnectSrc = ["'self'", ...validCorsOrigins];
 
+// M1: HSTS only makes sense over HTTPS. When serving plain HTTP (e.g. without
+// a TLS-terminating proxy), HSTS is ignored by browsers and can even cause
+// issues. Allow disabling it via HSTS_ENABLED=false (default: enabled in prod
+// when COOKIE_SECURE is true, i.e. when TLS is expected).
+const { COOKIE_SECURE } = require('./middleware/auth');
+const hstsEnabled = process.env.HSTS_ENABLED !== undefined
+  ? process.env.HSTS_ENABLED === 'true'
+  : COOKIE_SECURE;
+
 app.use(helmet({
   contentSecurityPolicy: {
     directives: {
@@ -71,12 +80,12 @@ app.use(helmet({
       fontSrc: ["'self'", "data:"],
     },
   },
-  // P18: HSTS - enforce HTTPS in production
-  hsts: {
+  // P18: HSTS - enforce HTTPS in production (only effective over HTTPS)
+  hsts: hstsEnabled ? {
     maxAge: 31536000,
     includeSubDomains: true,
     preload: true,
-  },
+  } : false,
   crossOriginEmbedderPolicy: false,
 }));
 
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deleted file mode 100644
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deleted file mode 100644
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diff --git a/backups/workflow_20260827_202650.sql.gz b/backups/workflow_20260827_202650.sql.gz
deleted file mode 100644
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diff --git a/backups/workflow_20260828_022649.sql.gz b/backups/workflow_20260828_022649.sql.gz
deleted file mode 100644
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diff --git a/docker-compose.stack.yml b/docker-compose.stack.yml
index f951ee6..4428eee 100644
--- a/docker-compose.stack.yml
+++ b/docker-compose.stack.yml
@@ -26,6 +26,8 @@ services:
       - LDAP_UPN_SUFFIX=${LDAP_UPN_SUFFIX:-}
       - ADMIN_EMAIL=${ADMIN_EMAIL:-admin@workflow.local}
       - ADMIN_INIT_PASSWORD=${ADMIN_INIT_PASSWORD:-}
+      # M3: Session-Secret für CSRF-Token-Ableitung (Pflicht in Produktion)
+      - SESSION_SECRET=${SESSION_SECRET:-}
       - CORS_ORIGIN=${CORS_ORIGIN:-}
       - NODE_ENV=${NODE_ENV:-production}
       - DATABASE_URL=postgresql://${POSTGRES_USER:-workflow}:${POSTGRES_PASSWORD:-workflow}@db:5432/${POSTGRES_DB:-workflow}
diff --git a/docker-compose.yml b/docker-compose.yml
index 35ec203..90a519d 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -20,6 +20,8 @@ services:
       - LDAP_UPN_SUFFIX=${LDAP_UPN_SUFFIX:-}
       - ADMIN_EMAIL=${ADMIN_EMAIL:-admin@workflow.local}
       - ADMIN_INIT_PASSWORD=${ADMIN_INIT_PASSWORD:-}
+      # M3: Session-Secret für CSRF-Token-Ableitung (Pflicht in Produktion)
+      - SESSION_SECRET=${SESSION_SECRET:-}
       - CORS_ORIGIN=${CORS_ORIGIN:-http://localhost:5000}
       - NODE_ENV=${NODE_ENV:-production}
       # Punkt 4: PostgreSQL (auto-started)
diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index 114dca8..5042dab 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -42,7 +42,7 @@ function AppContent() {
 
   // #13: Map tab IDs to display labels for mobile navbar indicator
   const tabLabels = {
-    dashboard: 'Vorlagen',
+    dashboard: 'Dashboard',
     templates: 'Vorlageneditor',
     tasks: 'Aufgaben',
     users: 'Nutzerverwaltung',
@@ -80,21 +80,21 @@ function AppContent() {
   const renderPages = () => (
     <>
       {/* Dashboard is always rendered for all users */}
-      <div className={activeTab === 'dashboard' ? 'block' : 'hidden'}>
+      <div className={activeTab === 'dashboard' ? 'h-full flex flex-col min-h-0' : 'hidden'}>
         <Dashboard onNavigate={handleTabChange} />
       </div>
       {isAdmin && (
         <>
-          <div className={activeTab === 'templates' ? 'block' : 'hidden'}>
+          <div className={activeTab === 'templates' ? 'h-full flex flex-col min-h-0' : 'hidden'}>
             <TemplatesPage />
           </div>
-          <div className={activeTab === 'tasks' ? 'block' : 'hidden'}>
+          <div className={activeTab === 'tasks' ? 'h-full flex flex-col min-h-0' : 'hidden'}>
             <TasksPage />
           </div>
-          <div className={activeTab === 'users' ? 'block' : 'hidden'}>
+          <div className={activeTab === 'users' ? 'h-full flex flex-col min-h-0' : 'hidden'}>
             <UsersPage />
           </div>
-          <div className={activeTab === 'auditlog' ? 'block' : 'hidden'}>
+          <div className={activeTab === 'auditlog' ? 'h-full flex flex-col min-h-0' : 'hidden'}>
             <AuditLogPage />
           </div>
         </>
@@ -106,10 +106,10 @@ function AppContent() {
   );
 
   return (
-    <div className="drawer lg:drawer-open">
+    <div className="drawer lg:drawer-open h-screen overflow-hidden">
       <input id="sidebar-drawer" type="checkbox" className="drawer-toggle" />
 
-      <div className="drawer-content flex flex-col">
+      <div className="drawer-content flex flex-col h-screen">
         {/* Mobile navbar */}
         <div className="lg:hidden navbar bg-base-100 shadow-md px-4 sticky top-0 z-30">
           <label htmlFor="sidebar-drawer" className="btn btn-square btn-ghost drawer-button">
@@ -120,10 +120,10 @@ function AppContent() {
           <span className="ml-2 font-bold">{tabLabels[activeTab] || 'Workflow Portal'}</span>
         </div>
 
-        {/* Main content */}
-        <main className="flex-1 overflow-auto bg-base-100">
+        {/* Main content — h-full für flex-1 Listen in den Seiten */}
+        <main className="flex-1 min-h-0 overflow-auto bg-base-100">
           <ErrorBoundary>
-            <div>
+            <div className="h-full flex flex-col">
               {renderPages()}
             </div>
           </ErrorBoundary>
diff --git a/frontend/src/components/FillModal.jsx b/frontend/src/components/FillModal.jsx
index 0e60295..1e9dc2c 100644
--- a/frontend/src/components/FillModal.jsx
+++ b/frontend/src/components/FillModal.jsx
@@ -1,7 +1,7 @@
 import React, { useState, useEffect, useRef } from 'react';
 import { useAuth } from '../context/AuthContext';
 import { useToast, ConfirmModal } from './Toast';
-import { apiFetch, FILE_BASE } from '../utils/api';
+import { apiFetch } from '../utils/api';
 
 export default function FillModal({ template, onSubmit, onClose }) {
   const { user: currentUser } = useAuth();
diff --git a/frontend/src/components/Sidebar.jsx b/frontend/src/components/Sidebar.jsx
index f01b174..87c295f 100644
--- a/frontend/src/components/Sidebar.jsx
+++ b/frontend/src/components/Sidebar.jsx
@@ -26,7 +26,7 @@ export default function Sidebar({ activeTab, onTabChange }) {
   const [collapsed, setCollapsed] = useState(false);
 
   const tabs = [
-    { id: 'dashboard', label: 'Vorlagen' },
+    { id: 'dashboard', label: 'Dashboard' },
     // Vorlageneditor nur für Admins sichtbar
     ...(user?.role === 'admin' ? [{ id: 'templates', label: 'Vorlageneditor' }] : []),
     ...(user?.role === 'admin' ? [{ id: 'tasks', label: 'Aufgaben' }] : []),
diff --git a/frontend/src/components/TaskModal.jsx b/frontend/src/components/TaskModal.jsx
index 4d7bfdf..426a289 100644
--- a/frontend/src/components/TaskModal.jsx
+++ b/frontend/src/components/TaskModal.jsx
@@ -1,5 +1,5 @@
 import React, { useEffect, useState } from 'react';
-import { apiFetch, FILE_BASE } from '../utils/api';
+import { apiFetch, safeFileUrl } from '../utils/api';
 import { useToast, ConfirmModal } from './Toast';
 
 const CUSTOM_STEP_TYPES = [
@@ -843,13 +843,13 @@ export default function TaskModal({ task, currentUserRole, onClose, onTaskUpdate
               );
             })}
 
-            {/* File attachment */}
-            {task.file_path && (
+            {/* File attachment — H1: nur validierte Upload-Pfade als Link */}
+            {safeFileUrl(task.file_path) && (
               <div className="mb-4">
                 <h4 className="font-semibold text-sm opacity-70 mb-2">Dateianhang</h4>
                 <div className="bg-base-200 p-3 rounded-lg">
                   <a
-                    href={`${FILE_BASE}${task.file_path}`}
+                    href={safeFileUrl(task.file_path)}
                     target="_blank"
                     rel="noopener noreferrer"
                     className="btn btn-outline btn-sm"
@@ -861,7 +861,7 @@ export default function TaskModal({ task, currentUserRole, onClose, onTaskUpdate
               </div>
             )}
 
-            {(!task.values || task.values.length === 0) && !task.file_path && (
+            {(!task.values || task.values.length === 0) && !safeFileUrl(task.file_path) && (
               <div className="text-center py-4 opacity-50">Keine Werte vorhanden.</div>
             )}
 
diff --git a/frontend/src/components/TemplateCard.jsx b/frontend/src/components/TemplateCard.jsx
index b4afe9b..acb5ec6 100644
--- a/frontend/src/components/TemplateCard.jsx
+++ b/frontend/src/components/TemplateCard.jsx
@@ -1,7 +1,9 @@
 import React from 'react';
 import { useAuth } from '../context/AuthContext';
 
-export default function TemplateCard({ template, onOpen, onEdit, onDelete }) {
+// action: optionales Action-Element (z.B. "Starten"-Button im Dashboard).
+// Wenn gesetzt, ersetzt es die Admin-Aktionen (Bearbeiten/Löschen).
+export default function TemplateCard({ template, onOpen, onEdit, onDelete, action }) {
   const { user } = useAuth();
   const isAdmin = user?.role === 'admin';
 
@@ -22,7 +24,9 @@ export default function TemplateCard({ template, onOpen, onEdit, onDelete }) {
           </p>
         </div>
         <div className="flex items-center gap-2 flex-shrink-0">
-          {isAdmin && (
+          {action ? (
+            action
+          ) : isAdmin && (
             <>
               <button className="btn btn-outline btn-sm" onClick={() => onEdit(template)}>
                 Bearbeiten
diff --git a/frontend/src/pages/Dashboard.jsx b/frontend/src/pages/Dashboard.jsx
index 4f7216a..04b0d2f 100644
--- a/frontend/src/pages/Dashboard.jsx
+++ b/frontend/src/pages/Dashboard.jsx
@@ -2,6 +2,7 @@ import React, { useState, useEffect, useCallback } from 'react';
 import { useAuth } from '../context/AuthContext';
 import { useToast } from '../components/Toast';
 import FillModal from '../components/FillModal';
+import TemplateCard from '../components/TemplateCard';
 import { apiFetch } from '../utils/api';
 
 export default function Dashboard({ onNavigate }) {
@@ -13,6 +14,9 @@ export default function Dashboard({ onNavigate }) {
   const [search, setSearch] = useState('');
   const [loading, setLoading] = useState(true);
   const [fillTemplate, setFillTemplate] = useState(null);
+  // Pagination für die Vorlagen-Table-Liste (10 Einträge pro Seite)
+  const TEMPLATES_PER_PAGE = 10;
+  const [currentPage, setCurrentPage] = useState(1);
 
   const fetchTemplates = useCallback(async () => {
     try {
@@ -52,6 +56,12 @@ export default function Dashboard({ onNavigate }) {
     t.name.toLowerCase().includes(search.toLowerCase()) ||
     (t.description || '').toLowerCase().includes(search.toLowerCase())
   );
+  // Pagination: Suchwechsel setzt auf Seite 1 zurück
+  const totalPages = Math.max(Math.ceil(filtered.length / TEMPLATES_PER_PAGE), 1);
+  const pagedTemplates = filtered.slice((currentPage - 1) * TEMPLATES_PER_PAGE, currentPage * TEMPLATES_PER_PAGE);
+  useEffect(() => {
+    setCurrentPage(1);
+  }, [search]);
 
   const handleSubmitTask = async (payload) => {
     const res = await apiFetch('/tasks', {
@@ -160,42 +170,11 @@ export default function Dashboard({ onNavigate }) {
         </section>
       )}
 
-      {/* Haupt-Grid: Top-Vorlagen (links) | Vorlagen mit Suche (rechts) */}
-      <div className="grid grid-cols-1 lg:grid-cols-12 gap-8 items-start">
-        {/* Linke Spalte: Top-Vorlagen Rangliste */}
-        {isAdmin && topTemplates.length > 0 && (
-          <section className="lg:col-span-4">
-            <div className="flex items-center justify-between mb-4 h-[38px]">
-              <h2 className="text-xl font-medium tracking-tight">Meistgenutzte Vorlagen</h2>
-            </div>
-            <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden">
-              <div className="divide-y divide-base-300">
-                {topTemplates.map((t) => (
-                  <div
-                    key={t.id}
-                    className="p-4 flex items-center justify-between hover:bg-base-300/50 transition-colors"
-                  >
-                    <div className="flex flex-col min-w-0">
-                      <span className="text-sm font-medium truncate">{t.name}</span>
-                      <span className="text-xs opacity-60">{t.task_count} Aufgaben</span>
-                    </div>
-                    <span className={`text-[10px] font-mono py-1 px-2 rounded shrink-0 ml-3 ${
-                      t.rank === 1 || t === topTemplates[0]
-                        ? 'bg-primary/10 text-primary border border-primary/20'
-                        : 'bg-base-300 text-base-content/60'
-                    }`}>
-                      TOP {topTemplates.indexOf(t) + 1}
-                    </span>
-                  </div>
-                ))}
-              </div>
-            </div>
-          </section>
-        )}
-
-        {/* Rechte Spalte: Vorlagen mit Suchleiste + Grid */}
-        <section className={isAdmin && topTemplates.length > 0 ? "lg:col-span-8" : "lg:col-span-12"}>
-          <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4 mb-4 h-[38px]">
+      {/* Haupt-Grid: Vorlagen-Liste (links) | Graph-Card (rechts) — gleich große Spalten */}
+      <div className="grid grid-cols-1 lg:grid-cols-2 gap-8 items-stretch">
+        {/* Linke Spalte: Vorlagen als Table-Liste */}
+        <section aria-label="Vorlagen" className="flex flex-col">
+          <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4 mb-4">
             <h2 className="text-xl font-medium tracking-tight">{isAdmin ? 'Vorlagen' : 'Verfügbare Vorlagen'}</h2>
             <div className="form-control w-full sm:w-72">
               <input
@@ -217,34 +196,96 @@ export default function Dashboard({ onNavigate }) {
               <p className="text-sm opacity-60">Keine Vorlagen für „{search}" gefunden.</p>
             </div>
           ) : (
-            <div className="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-4 gap-3">
-              {filtered.map((tpl) => {
-                const pageCount = [...new Set(tpl.steps?.map((s) => s.page_num) || [])].length;
-                return (
-                  <article key={tpl.id} className="card bg-base-200 shadow-sm hover:shadow-md transition-all rounded-lg p-4 flex flex-col justify-between min-h-32">
-                    <div>
-                      {pageCount > 1 && (
-                        <div className="flex justify-end mb-2">
-                          <span className="text-[10px] opacity-50 font-mono">{pageCount} Seiten</span>
-                        </div>
-                      )}
-                      <h3 className="text-base font-medium line-clamp-2 leading-tight">{tpl.name}</h3>
-                    </div>
-                    <div className="flex items-center justify-end mt-3">
-                      <button
-                        className="btn btn-primary btn-sm"
-                        onClick={() => setFillTemplate(tpl)}
-                      >
-                        <svg xmlns="http://www.w3.org/2000/svg" className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M14.752 11.168l-3.197-2.132A1 1 0 0010 9.87v4.263a1 1 0 001.555.832l3.197-2.132a1 1 0 000-1.664z" /><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" /></svg>
-                        Starten
-                      </button>
-                    </div>
-                  </article>
-                );
-              })}
-            </div>
+            <>
+              {/* Scrollbare Liste — flex-1 + min-h-0 (Pflicht für overflow in Flexbox),
+                  damit die Liste innerhalb der Card-Höhe scrollt statt sie aufzuspannen */}
+              <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden flex-1 flex flex-col min-h-[600px] max-h-[600px]">
+                <div className="divide-y divide-base-300 flex-1 min-h-0 overflow-y-auto">
+                  {pagedTemplates.map((tpl) => (
+                    <TemplateCard
+                      key={tpl.id}
+                      template={tpl}
+                      action={
+                        <button
+                          className="btn btn-primary btn-sm"
+                          onClick={() => setFillTemplate(tpl)}
+                        >
+                          <svg xmlns="http://www.w3.org/2000/svg" className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M14.752 11.168l-3.197-2.132A1 1 0 0010 9.87v4.263a1 1 0 001.555.832l3.197-2.132a1 1 0 000-1.664z" /><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" /></svg>
+                          Starten
+                        </button>
+                      }
+                    />
+                  ))}
+                </div>
+              </div>
+
+              {/* Pagination: 10 Vorlagen pro Seite */}
+              {totalPages > 1 && (
+                <div className="flex justify-center items-center gap-2 mt-4">
+                  <button
+                    className="btn btn-sm btn-outline"
+                    disabled={currentPage <= 1}
+                    onClick={() => setCurrentPage((p) => Math.max(p - 1, 1))}
+                  >
+                    « Zurück
+                  </button>
+                  <span className="text-sm opacity-70">
+                    Seite {currentPage} von {totalPages}
+                  </span>
+                  <button
+                    className="btn btn-sm btn-outline"
+                    disabled={currentPage >= totalPages}
+                    onClick={() => setCurrentPage((p) => Math.min(p + 1, totalPages))}
+                  >
+                    Weiter »
+                  </button>
+                </div>
+              )}
+            </>
           )}
         </section>
+
+        {/* Rechte Spalte: Meistgenutzte Vorlagen als Column-Chart (Anteil in %) */}
+        {isAdmin && topTemplates.length > 0 && (
+          <section aria-label="Meistgenutzte Vorlagen" className="flex flex-col">
+            {/* Header mit gleicher Mindesthöhe wie der Listen-Header (Suchbox = 48px),
+                damit beide Cards auf derselben Höhe starten */}
+            <div className="flex items-center justify-between mb-4 sm:min-h-[48px]">
+              <h2 className="text-xl font-medium tracking-tight">Meistgenutzt</h2>
+            </div>
+            <div className="card bg-base-200 shadow-sm rounded-xl flex-1 flex flex-col">
+              <div className="card-body p-5 flex-1 flex flex-col justify-center">
+                {(() => {
+                  // Prozentanteil jeder Vorlage an allen Task-Zuordnungen der Top-Liste
+                  const totalCount = topTemplates.reduce((sum, t) => sum + (t.task_count || 0), 0);
+                  if (totalCount === 0) return null;
+                  return (
+                    <div className="flex items-end justify-around gap-2 sm:gap-4 h-64 pt-2">
+                      {topTemplates.map((t, idx) => {
+                        const pct = Math.round(((t.task_count || 0) / totalCount) * 100);
+                        return (
+                          <div key={t.id} className="flex flex-col items-center justify-end h-full flex-1 min-w-0">
+                            {/* Prozentwert über der Säule */}
+                            <span className="text-xs font-semibold tabular-nums mb-1">{pct}%</span>
+                            {/* Säule: Höhe proportional zum Prozentanteil, animiert per CSS-Transition */}
+                            <div
+                              className={`w-full max-w-16 rounded-t-md transition-all duration-700 ${idx === 0 ? 'bg-primary' : 'bg-primary/50'}`}
+                              style={{ height: `${Math.max(pct, 2)}%` }}
+                            />
+                            {/* Beschriftung unter der Säule */}
+                            <span className="text-[11px] opacity-70 truncate w-full text-center mt-2" title={t.name}>
+                              {t.name}
+                            </span>
+                          </div>
+                        );
+                      })}
+                    </div>
+                  );
+                })()}
+              </div>
+            </div>
+          </section>
+        )}
       </div>
 
       {fillTemplate && (
diff --git a/frontend/src/pages/TasksPage.jsx b/frontend/src/pages/TasksPage.jsx
index d81f9d3..6db0eb5 100644
--- a/frontend/src/pages/TasksPage.jsx
+++ b/frontend/src/pages/TasksPage.jsx
@@ -2,7 +2,7 @@ import React, { useState, useEffect, useCallback } from 'react';
 import { useAuth } from '../context/AuthContext';
 import { useToast, ConfirmModal } from '../components/Toast';
 import TaskModal from '../components/TaskModal';
-import { apiFetch, FILE_BASE } from '../utils/api';
+import { apiFetch, safeFileUrl } from '../utils/api';
 
 export default function TasksPage() {
   const { user } = useAuth();
@@ -107,7 +107,7 @@ export default function TasksPage() {
   }
 
   return (
-    <div className="p-4 md:p-6">
+    <div className="p-4 md:p-6 h-full flex flex-col min-h-0">
       <div className="flex flex-col sm:flex-row justify-between items-start sm:items-center gap-4 mb-6">
         <h2 className="text-2xl font-bold">Aufgaben</h2>
         <div className="flex flex-wrap items-center gap-2">
@@ -146,9 +146,11 @@ export default function TasksPage() {
           </div>
         </div>
       ) : (
-        <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden">
-          <div className="divide-y divide-base-300">
-            {filtered.map((task) => (
+        <>
+          {/* Scrollbare Table-Liste — füllt die restliche Seitenhöhe */}
+          <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden flex-1 min-h-0 flex flex-col">
+            <div className="divide-y divide-base-300 flex-1 min-h-0 overflow-y-auto">
+              {filtered.map((task) => (
               <div
                 key={task.id}
                 className="p-4 sm:p-5 hover:bg-base-300/40 transition-colors cursor-pointer"
@@ -168,11 +170,11 @@ export default function TasksPage() {
                         <span className="text-sm opacity-70">{task.template_name}</span>
                       )}
                     </div>
-                    {/* File attachments in row */}
-                    {task.file_path && (
+                    {/* File attachments in row — H1: nur validierte Upload-Pfade als Link */}
+                    {safeFileUrl(task.file_path) && (
                       <div className="mt-2">
                         <a
-                          href={`${FILE_BASE}${task.file_path}`}
+                          href={safeFileUrl(task.file_path)}
                           target="_blank"
                           rel="noopener noreferrer"
                           className="inline-flex items-center gap-1 text-sm text-primary hover:underline"
@@ -183,13 +185,13 @@ export default function TasksPage() {
                         </a>
                       </div>
                     )}
-                    {/* File attachments from task values */}
-                    {task.values?.filter(v => v.step_type === 'file_upload' && v.value).length > 0 && (
+                    {/* File attachments from task values — H1: nur validierte Upload-Pfade als Link */}
+                    {task.values?.filter(v => v.step_type === 'file_upload' && safeFileUrl(v.value)).length > 0 && (
                       <div className="mt-2 flex flex-wrap gap-2">
-                        {task.values.filter(v => v.step_type === 'file_upload' && v.value).map(v => (
+                        {task.values.filter(v => v.step_type === 'file_upload' && safeFileUrl(v.value)).map(v => (
                           <a
                             key={v.id}
-                            href={`${FILE_BASE}${v.value}`}
+                            href={safeFileUrl(v.value)}
                             target="_blank"
                             rel="noopener noreferrer"
                             className="inline-flex items-center gap-1 text-sm text-primary hover:underline"
@@ -223,8 +225,9 @@ export default function TasksPage() {
                 </div>
               </div>
             ))}
+            </div>
           </div>
-        </div>
+        </>
       )}
 
       {selectedTask && (
diff --git a/frontend/src/pages/TemplatesPage.jsx b/frontend/src/pages/TemplatesPage.jsx
index d6bcdd1..e958e43 100644
--- a/frontend/src/pages/TemplatesPage.jsx
+++ b/frontend/src/pages/TemplatesPage.jsx
@@ -124,7 +124,7 @@ export default function TemplatesPage() {
   }
 
   return (
-    <div className="p-6">
+    <div className="p-6 h-full flex flex-col min-h-0">
       <div className="flex items-center justify-between mb-6">
         <h2 className="text-2xl font-bold">Vorlageneditor</h2>
         {isAdmin && (
@@ -135,8 +135,9 @@ export default function TemplatesPage() {
         )}
       </div>
 
-      <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden">
-        <div className="divide-y divide-base-300">
+      {/* Scrollbare Table-Liste — füllt die restliche Seitenhöhe */}
+      <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden flex-1 min-h-0 flex flex-col">
+        <div className="divide-y divide-base-300 flex-1 min-h-0 overflow-y-auto">
           {templates.map((tpl) => (
             <TemplateCard
               key={tpl.id}
diff --git a/frontend/src/utils/api.js b/frontend/src/utils/api.js
index 6287b84..e882159 100644
--- a/frontend/src/utils/api.js
+++ b/frontend/src/utils/api.js
@@ -5,6 +5,18 @@ export const FILE_BASE = import.meta.env.VITE_API_BASE
   ? import.meta.env.VITE_API_BASE.replace(/\/api$/, '')
   : '';
 
+// H1: Sichere Download-URLs — nur Pfade, die exakt vom Upload-Endpoint stammen,
+// werden zu einer URL aufgelöst. Alles andere (javascript:, data:, absolute
+// URLs, Pfad-Traversal, ausführbare Endungen) gibt null zurück und wird im UI
+// nicht als Link gerendert. Spiegelt die serverseitige Whitelist in
+// backend/middleware/validation.js (inkl. Endungs-Beschränkung).
+const UPLOAD_PATH_PATTERN = /^\/api\/upload\/uploads\/[0-9]+-[0-9]+-[a-zA-Z0-9._-]*\.(pdf|png|jpg|jpeg|gif|txt|doc|docx|bin)$/;
+
+export function safeFileUrl(path) {
+  if (typeof path !== 'string' || !UPLOAD_PATH_PATTERN.test(path)) return null;
+  return `${FILE_BASE}${path}`;
+}
+
 // P5: CSRF token — the server derives it deterministically from the session and
 // self-heals the cookie on every GET. The frontend simply reads the cookie fresh
 // on every request, so memory/cookie can never drift apart (no more 403s).