10-01-2025, 12:30 PM
Medium
resolved
resolved
`use-mcp`'s oauth2 process uses a window.open call with untrusted mcp server provided data allowing for code execution under the page using it
Bug reported by Raymond was disclosed at September 30, 2025, 8:15 am | Cross-site Scripting (XSS) - Generic
The `authorizeEndpoint` parameter from `use-mcp` version was susceptible to XSS. Sanitization of that parameter was added in version 0.0.10 of use-mcp. A skilled attacker was able to turn this XSS into code execution on the client.