Koel Vulnerable to SSRF via Podcast Episode Enclosure URLs

Koel is a free, open-source music streaming solution. Prior to version 9.3.5, Koel validates the podcast feed URL via the SafeUrl rule (DNS resolution + public IP check), but the individual episode <enclosure url="..."> values extracted from the RSS XML are stored directly into the database without any SSRF validation. When a user plays an episode, the server downloads the full HTTP response from the unvalidated enclosure URL via Http::sink()->get() and streams it back to the user, enabling full-read SSRF against internal services. This issue has been patched in version 9.3.5.