Koel: Server-Side Request Forgery (SSRF) in radio station creation due to missing validation bail

Koel is a free, open-source music streaming solution. Prior to version 9.7.1, Koel contains a Server-Side Request Forgery (SSRF) vulnerability in the radio station creation endpoint (POST /api/radio/stations). The url field validation rules are declared without the bail keyword, so the HasAudioContentType rule — which issues HTTP requests to the supplied URL — still executes even after the SafeUrl rule has rejected the URL as pointing to a private/reserved address. Any authenticated, non-admin user can therefore coerce the server into making HEAD/GET requests to arbitrary internal hosts. This issue has been patched in version 9.7.1.