Formidable Digital Signatures <= 3.0.6 - Unauthenticated Arbitrary File Deletion via Signature Field

The Formidable Digital Signatures plugin for WordPress is vulnerable to file deletion due to insufficient file path validation in the delete_file function in all versions up to, and including, 3.0.6. This makes it possible for unauthenticated attackers to delete files on the server by supplying an attacker-controlled filename in the item_meta[field_id][content] parameter alongside the delete_saved_image flag during the standard entry-creation POST flow on any form that accepts anonymous submissions.