NextChat is a cross-platform ChatGPT/Gemini UI. There is a Server-Side Request Forgery (SSRF) vulnerability due to a lack of validation of the endpoint GET parameter on the WebDav API endpoint. This SSRF can be used to perform arbitrary HTTPS request from the vulnerable instance (MKCOL, PUT and GET methods supported), or to target NextChat users and make them execute arbitrary JavaScript code in their browser. This vulnerability has been patched in version 2.12.4.
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.