WP Directory Kit < 1.5.7 - Unauthenticated User Email Disclosure via select_2_ajax_user

The WP Directory Kit WordPress plugin before 1.5.7 does not perform any authorization check on one of its public AJAX actions and returns unfiltered database rows, allowing unauthenticated attackers to retrieve the usernames and email addresses of users holding the WP Directory Kit WordPress plugin before 1.5.7's own roles.