The Booking Calendar plugin for WordPress is vulnerable to unauthorized access of data due to a missing capability check on the wpbc_ajax_WPBC_FLEXTIMELINE_NAV() function in all versions up to, and including, 10.14.13. This makes it possible for unauthenticated attackers to retrieve booking information including customer names, phones and emails.
https://plugins.trac.wordpress.org/browser/booking/tags/10.14.13/core/lib/wpbc-ajax.php#L25