CVE-2026-33237: AVideo has SSRF in Scheduler Plugin via callbackURL Missing `isSSRFSafeURL()` Validation

The Scheduler plugin’s run() function in plugin/Scheduler/Scheduler.php calls url_get_contents() with an admin-configurable callbackURL that is validated only by isValidURL() (URL format check). Unlike other AVideo endpoints that were recently patched for SSRF (GHSA-9x67-f2v7-63rw, GHSA-h39h-7cvg-q7j6), the Scheduler’s callback URL is never passed through isSSRFSafeURL(), which blocks requests to RFC-1918 private addresses, loopback, and cloud metadata endpoints. An admin can configure a scheduled task with an internal network callbackURL to perform SSRF against cloud infrastructure metadata services or internal APIs not otherwise reachable from the internet.