The Filr – Secure document library plugin for WordPress is vulnerable to Stored Cross-Site Scripting via unrestricted file upload in all versions up to, and including, 1.2.11 due to insufficient file type restrictions in the FILR_Uploader class. This makes it possible for authenticated attackers, with Administrator-level access and above, to upload malicious HTML files containing JavaScript that will execute whenever a user accesses the uploaded file, granted they have permission to create or edit posts with the 'filr' post type.