CVE-2026-40909: WWBN AVideo has a Path Traversal in Locale Save Endpoint Enables Arbitrary PHP File Write to Any Web-Accessible Directory (RCE)

The locale save endpoint (locale/save.php) constructs a file path by directly concatenating $_POST['flag'] into the path at line 30 without any sanitization. The $_POST['code'] parameter is then written verbatim to that path via fwrite() at line 40. An admin attacker (or any user who can CSRF an admin, since no CSRF token is checked and cookies use SameSite=None) can traverse out of the locale/ directory and write arbitrary .php files to any writable location on the filesystem, achieving Remote Code Execution.