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.