fix: comprehensive security hardening and bug fixes across all codebases

[eren-karakus0]

Summary

Comprehensive security audit and bug fix pass across all four codebases (server, electron, frontend, backend). This PR addresses 22 issues including XSS vulnerabilities, IDOR access control gaps, authentication bypasses, race conditions, path traversal vectors, and runtime crashes.

Server Fixes (8)

• Reflected XSS in redirect callback — user-controlled code parameter injected unescaped into HTML response. Fixed with html.escape().
• KeyError crash in MCP install — bracket access on optional dict keys. Fixed with .get() defaults.
• IDOR on GET /mcp/users/{id} — missing user_id ownership filter allows any authenticated user to read other users' MCP configs. Added McpUser.user_id == user_id filter.
• IDOR on DELETE /mcp/users/{id} — no ownership check before deletion. Added 403 response for non-owners.
• Blocked user login bypass — by_password and dev_login endpoints don't check Status.Block. Added status check to both.
• auth_must None token crash — oauth2_scheme(auto_error=False) can pass None token, causing unhandled exception. Added None guard + user existence check.
• KeyError in grouped history — defaultdict factory missing total_failed_tasks key. Added with default 0.
• Path traversal in snapshot save — api_task_id used directly in os.path.join without sanitization. Added regex whitelist + realpath boundary check.

Electron Fixes (5)

• Disabled code signature verification — verifyUpdateCodeSignature was set to false, allowing unsigned updates. Changed to true.
• XSS in file parsers — xlsx, csv, pptx cell content rendered as raw HTML. Added escapeHtml() utility function.
• Event listener accumulation — startDownload adds new listeners each call without cleanup, causing memory leaks. Added removeAllListeners() + .once().
• Arbitrary file execution — shell.openPath() executes files; changed to shell.showItemInFolder() for directory reveal.
• OAuth token leak in logs — authorization code logged in plaintext. Replaced with [REDACTED].

Frontend Fixes (5)

• Division by zero — taskProgress calculation crashes when taskRunning is empty. Added denominator === 0 guard.
• XSS via dangerouslySetInnerHTML — input.tsx and textarea.tsx render user-influenced HTML without sanitization. Wrapped with DOMPurify.sanitize().
• Weak RNG for IDs — generateUniqueId() used Math.random(). Replaced with crypto.getRandomValues().
• Secret key client exposure — hasStackKeys() checked VITE_STACK_SECRET_SERVER_KEY, leaking server secret to browser bundle. Removed.

Backend Fixes (4)

• TOCTOU race condition — task_locks dict accessed from multiple threads without synchronization. Added threading.Lock mutex to create_task_lock and get_or_create_task_lock.
• Predictable temp file — cookie_manager used fixed .tmp suffix, vulnerable to symlink attacks. Replaced with tempfile.mkstemp().
• Absolute path traversal — sanitize_env_path accepted absolute paths that could escape ~/.eigent. Now rejects all absolute paths outright.
• Lock bypass in OAuthStateManager — tool_controller.py accessed _states dict directly, bypassing the threading lock. Added remove_state() method.

Test Plan

• 13 new pytest tests for server security fixes (server/tests/test_security_fixes.py)
• 4 new pytest tests for task lock mutex thread safety (backend/tests/app/service/test_task_lock_mutex.py)
• 6 new pytest tests for OAuth state manager lifecycle (backend/tests/app/utils/test_oauth_state_manager.py)
• 2 new pytest tests for cookie manager temp file uniqueness (backend/tests/app/utils/test_cookie_manager.py)
• 1 existing test updated for absolute path rejection (backend/tests/app/component/test_environment.py)
• 4 new vitest tests for CSPRNG ID generation and secret key removal (test/unit/lib/securityFixes.test.ts)
• 7 new vitest tests for escapeHtml utility (test/unit/electron/fileReader.test.ts)
• 6 new vitest tests for division-by-zero guard (test/unit/store/chatStore-divisionByZero.test.ts)

Total: 43 new tests across pytest and vitest

[bytecii]

Can you split the pr? Thanks.

[eren-karakus0]

Closed in favor of split PRs as requested:

• fix(backend): security hardening for environment, cookies, oauth, and task locking #1311 — Backend: environment, cookies, oauth, task locking
• fix(server): harden auth, MCP, redirect, and snapshot endpoints #1312 — Server: auth, MCP, redirect, snapshot endpoints
• fix(frontend): security hardening for Electron, UI inputs, and store logic #1313 — Frontend/Electron: fileReader, UI inputs, chatStore, URL sanitization

Each PR is now scoped to a single codebase for easier review.