WP Contact Form 7 DB Handler <= 3.0 - Cross-Site Request Forgery to Arbitrary File Deletion via 'contact_form' Parameter

Summary

The WP Contact Form 7 DB Handler plugin for WordPress is vulnerable to Cross-Site Request Forgery leading to Arbitrary File Deletion via SQL Injection and PHP Object Injection in versions up to and including 3.0. This is due to a missing nonce verification in the process_bulk_action() function, the nonce check is only executed when _wpnonce is present in the POST body, allowing it to be trivially bypassed by omitting the field, combined with the use of an unsanitized, unparameterized user-supplied value in a numeric SQL context (WHERE ID = $ID) and the unsafe deserialization of the query result's post_content field. An attacker can craft a CSRF page that tricks a logged-in administrator into triggering a UNION-based SQL injection payload (using CHAR() to avoid esc_sql quote-escaping) that returns a malicious serialized PHP array as post_content; upon deserialization, array values associated with keys containing 'ys_cfdbh_file' are used as file paths appended to the uploads directory path without any path traversal validation, and then passed to wp_delete_file(), allowing the attacker to delete arbitrary files on the server (e.g., wp-config.php, system files).