GHSA-w3hv-x4fp-6h6j

### Impact

The WebSocket upgrade handler in the server validates authentication (API key token or session cookie) but does not check the `Origin` header. A malicious webpage on a different origin could initiate a WebSocket connection to `ws://localhost:3000/ws` if it can leverage the user's session cookie (which is `SameSite=Lax`, allowing top-level navigations).

This enables **cross-origin WebSocket hijacking** — if a user visits a malicious site while a Grackle session is active, the attacker's page could open a WebSocket and subscribe to real-time events (session output, task updates, environment state).

**Affected code:** - `packages/server/src/ws-bridge.ts:80-91` — connection handler accepts WebSocket upgrades without checking `req.headers.origin`

### Patches

**Fix:** Validate `req.headers.origin` against an allowlist before accepting connections: ```typescript const origin = req.headers.origin || ""; if (origin && !origin.includes("localhost") && !origin.includes("127.0.0.1")) { ws.close(4003, "Invalid origin"); return; } ```

### Workarounds

Ensure the Grackle server is only accessible on `127.0.0.1` (the default). Do not use `--allow-network` in untrusted network environments.

### Resources

- CWE-346: Origin Validation Error - File: `packages/server/src/ws-bridge.ts`