CVE-2026-33493: fallo de gravedad alta en WWBN AVideo

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the `objects/import.json.php` endpoint accepts a user-controlled `fileURI` POST parameter with only a regex check that the value ends in `.mp4`. Unlike `objects/listFiles.json.php`, which was hardened with a `realpath()` + directory prefix check to restrict paths to the `videos/` directory, `import.json.php` performs no directory restriction. This allows an authenticated user with upload permission to: (1) steal any other user's private video files by importing them into their own account, (2) read `.txt`/`.html`/`.htm` files adjacent to any `.mp4` file on the filesystem, and (3) delete `.mp4` and adjacent text files if writable by the web server process. Commit e110ff542acdd7e3b81bdd02b8402b9f6a61ad78 contains a patch.