The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 1.6.8.5. This is due to the software allowing users to execute an action that does not properly validate a value before running doshortcode. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes.

The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to denial of service in all versions up to, and including, 1.6.11.5. This is due to a publicly accessible REST API endpoint (/wp-json/ssa/v1/async) that calls PHP's sleep() function on a user-supplied delay parameter without any rate limiting. This makes it possible for unauthenticated attackers to exhaust PHP worker processes, denying access to the site to legitimate users.