CVE-2026-56345: AVideo - Arbitrary User Session Hijacking via Meet Plugin uploadRecordedVideo Endpoint

AVideo through 29.0 contains an authorization bypass vulnerability in the Meet plugin's uploadRecordedVideo.json.php endpoint that derives the target usersid from the uploaded filename without verification. An attacker with knowledge of the Meet shared secret can craft a malicious file upload with a filename containing an arbitrary usersid to invoke passwordless User->login() and establish an authenticated session as any user including admin. Attackers can obtain the Meet shared secret through path-traversal vulnerabilities or timing attacks against checkToken.json.php, then POST a crafted file to uploadRecordedVideo.json.php with a filename like '1-anything.mp4' to hijack admin sessions and gain full account takeover.