The WP-Optimize plugin for WordPress is vulnerable to unauthorized access of functionality due to missing capability checks in the receive_heartbeat() function in includes/class-wp-optimize-heartbeat.php in all versions up to, and including, 4.5.0. This is due to the Heartbeat handler directly invoking Updraft_Smush_Manager_Commands methods without verifying user capabilities, nonce tokens, or the allowed commands whitelist that the normal AJAX handler (updraft_smush_ajax) enforces. This makes it possible for authenticated attackers, with Subscriber-level access and above, to invoke admin-only Smush operations including reading log files (get_smush_logs), deleting all backup images (clean_all_backup_images), triggering bulk image processing (process_bulk_smush), and modifying Smush options (update_smush_options).