AVideo has SSRF in BulkEmbed Thumbnail Fetch that Allows Reading Internal Network Resources

WWBN AVideo is an open source video platform. Prior to version 26.0, the BulkEmbed plugin's save endpoint (`plugin/BulkEmbed/save.json.php`) fetches user-supplied thumbnail URLs via `url_get_contents()` without SSRF protection. Unlike all six other URL-fetching endpoints in AVideo that were hardened with `isSSRFSafeURL()`, this code path was missed. An authenticated attacker can force the server to make HTTP requests to internal network resources and retrieve the responses by viewing the saved video thumbnail. Version 26.0 fixes the issue.