fix(security): harden Live Components with 4 high-priority security improvements#64
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MarcosBrendonDePaula merged 5 commits intomainfrom Feb 21, 2026
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…mprovements 1. Anti-replay on rehydration: Add cryptographic nonce to signed state. Each signed state now includes a random 128-bit nonce that is consumed on validation, preventing the same signed state from being replayed. Expired nonces are cleaned up daily to prevent memory growth. 2. Magic bytes content validation for uploads: Validate actual file content against known magic byte signatures (JPEG, PNG, GIF, WebP, PDF, ZIP, GZIP) instead of trusting only the MIME type header. Also detect double extension bypass attacks (e.g., malware.exe.jpg). 3. Per-user upload quota: Enforce 500MB/day upload limit per user to prevent disk exhaustion attacks. Quotas are tracked by userId and reset daily. 4. Mandatory publicActions whitelist: Components without publicActions now deny ALL remote actions (secure by default). Previously, missing publicActions would fall back to blocklist-only mode which is more fragile. All existing components updated with explicit publicActions declarations. https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3
- Component generator (make:live): All 4 templates now include static publicActions with the appropriate methods listed - LLMD/resources/live-components.md: publicActions documented as mandatory in Quick Facts, class structure, Actions section, setValue note, component organization, and Critical Rules - LLMD/resources/live-upload.md: Added Security Features section with magic bytes table, per-user quota docs, double extension prevention, updated chunked upload flow, and error handling examples - LLMD/patterns/anti-patterns.md: New "Live Component Security Anti-Patterns" section covering missing publicActions, unsafe setValue usage, MIME type trust, and double extensions - LLMD/resources/live-auth.md: Added publicActions to all code examples, new "Security Layers" section documenting action execution order, updated auth flow diagram and Critical Rules https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3
The client-side ExtractActions<T> type previously extracted ALL public async methods from the server component class, ignoring publicActions. This caused TypeScript to autocomplete methods that the server would reject at runtime. Now: - If publicActions is defined: only those methods appear in the type - If publicActions is NOT defined: Record<string, never> (no actions) This matches the server-side enforcement where components without publicActions deny ALL remote actions (secure by default). https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3
Adds a $private key-value store on LiveComponent that never syncs with the client. Sensitive data like tokens and API keys can now be stored server-side without leaking via STATE_UPDATE/STATE_DELTA messages. - Add _privateState field and $private getter to LiveComponent - Block $private and _privateState in BLOCKED_ACTIONS and forbidden set - Clear _privateState on destroy() - Add 16 tests covering isolation, security, and lifecycle - Update live-components.md and anti-patterns.md docs https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3
The second generic parameter on LiveComponent enables full autocomplete
and type checking for server-only private state. Defaults to
Record<string, any> so existing components need no changes.
Usage: LiveComponent<State, { token: string; apiKey: string }>
- Add TPrivate generic with default Record<string, any>
- Add InferPrivateState<T> utility type
- Add typed $private tests (22 total, 6 new)
- Update live-components.md with typed $private section
- TypeScript compilation passes with zero errors
https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3
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Anti-replay on rehydration: Add cryptographic nonce to signed state.
Each signed state now includes a random 128-bit nonce that is consumed
on validation, preventing the same signed state from being replayed.
Expired nonces are cleaned up daily to prevent memory growth.
Magic bytes content validation for uploads: Validate actual file content
against known magic byte signatures (JPEG, PNG, GIF, WebP, PDF, ZIP, GZIP)
instead of trusting only the MIME type header. Also detect double extension
bypass attacks (e.g., malware.exe.jpg).
Per-user upload quota: Enforce 500MB/day upload limit per user to prevent
disk exhaustion attacks. Quotas are tracked by userId and reset daily.
Mandatory publicActions whitelist: Components without publicActions now
deny ALL remote actions (secure by default). Previously, missing
publicActions would fall back to blocklist-only mode which is more fragile.
All existing components updated with explicit publicActions declarations.
https://claude.ai/code/session_0193vWzJM26QCwN4K9P7rQP3