CVE-2026-16585: Better Messages <= 2.15.19 - Authenticated (Administrator+) Arbitrary File Deletion via Path Traversal via 'file' Parameter

The Better Messages – Chat Rooms, Group Chat, Private Messages & AI Chat Bots plugin for WordPress is vulnerable to arbitrary file deletion due to insufficient file path validation in the deletesticker function in all versions up to, and including, 2.15.19. This makes it possible for authenticated attackers, with administrator-level access and above, to delete arbitrary files on the server, which can easily lead to remote code execution when the right file is deleted (such as wp-config.php). The prefix check intended to restrict deletion to the uploads directory can be bypassed by crafting a URL that begins with the legitimate uploads base URL but embeds ../ traversal sequences in the path portion, as the normalizesticker function only applies escurlraw(), which does not strip ../ sequences, allowing the traversal payload to be stored verbatim in WordPress options.