GHSA-cf57-c578-7jvv

### Summary When using subrequest authentication, Anubis did not perform validation of the redirect URL and redirects user to any URL scheme. While most modern browsers do not allow a redirect to `javascript:` URLs, it could still trigger dangerous behavior in some cases. `GET https://example.com/.within.website/?redir=javascript:alert()` responds with `Location: javascript:alert()`. ### Impact Anybody with a subrequest authentication seems affected. Using `javascript:` URLs will probably be blocked by most modern browsers, but using custom protocols for third-party applications might still trigger dangerous operations. ### Note This was originally reported by @mbiesiad against Weblate.