Booking Calendar <= 10.14.10 - Unauthenticated Sensitive Information Exposure

The Booking Calendar plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 10.14.10 via the `WPBC_FLEXTIMELINE_NAV` AJAX action. This is due to the nonce verification being conditionally disabled by default (`booking_is_nonce_at_front_end` option is `'Off'` by default). When the `booking_is_show_popover_in_timeline_front_end` option is enabled (which is the default in demo installations and can be enabled by administrators), it is possible for unauthenticated attackers to extract sensitive booking data including customer names, email addresses, phone numbers, and booking details.