Avada (Fusion) Builder <= 3.15.3 - Unauthenticated Arbitrary File Deletion

The Avada (Fusion) Builder plugin for WordPress is vulnerable to arbitrary file deletion due to insufficient file path validation in the maybe_delete_files function in all versions up to, and including, 3.15.3. This makes it possible for unauthenticated attackers 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 attack requires a published Avada form configured to save entries to the database; an unauthenticated attacker submits a path-traversal payload via the wp_ajax_nopriv_fusion_form_submit_ajax handler while also controlling the fusion_privacy_expiration_interval and privacy_expiration_action fields to force an immediate 'delete' cleanup, causing the planted entry to be automatically processed by the Fusion_Form_DB_Privacy shutdown-hook routine without any administrator interaction.