A PinchTab Security Policy Bypass in /wait Allows Arbitrary JavaScript Execution

PinchTab is a standalone HTTP server that gives AI agents direct control over a Chrome browser. PinchTab v0.8.3 through v0.8.5 allow arbitrary JavaScript execution through POST /wait and POST /tabs/{id}/wait when the request uses fn mode, even if security.allowEvaluate is disabled. POST /evaluate correctly enforces the security.allowEvaluate guard, which is disabled by default. However, in the affected releases, POST /wait accepted a user-controlled fn expression, embedded it directly into executable JavaScript, and evaluated it in the browser context without checking the same policy. This is a security-policy bypass rather than a separate authentication bypass. Exploitation still requires authenticated API access, but a caller with the server token can execute arbitrary JavaScript in a tab context even when the operator explicitly disabled JavaScript evaluation. The current worktree fixes this by applying the same policy boundary to fn mode in /wait that already exists on /evaluate, while preserving the non-code wait modes. As of time of publication, a patched version is not yet available.