AVideo Vulnerable to Remote Code Execution via MIME/Extension Mismatch in ImageGallery File Upload

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the ImageGallery::saveFile() method validates uploaded file content using finfo MIME type detection but derives the saved filename extension from the user-supplied original filename without an allowlist check. An attacker can upload a polyglot file (valid JPEG magic bytes followed by PHP code) with a .php extension. The MIME check passes, but the file is saved as an executable .php file in a web-accessible directory, achieving Remote Code Execution. Commit 345a8d3ece0ad1e1b71a704c1579cbf885d8f3ae contains a patch.