The WP CTA – Sticky CTA Builder, Generate Leads, Promote Sales plugin for WordPress is vulnerable to time-based blind SQL Injection via the 'fildname' parameter in all versions up to, and including, 2.2.2. This is due to insufficient escaping of user-supplied column names in the ajaxCheck() method and lack of preparation in the $wpdb->update() call. The vulnerability is compounded by the complete absence of authorization checks and the endpoint being registered for unauthenticated users via wp_ajax_nopriv_. This makes it possible for unauthenticated attackers to inject arbitrary SQL queries and extract sensitive information from the database via time-based blind SQL injection techniques, including administrator password hashes.