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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Simply Schedule Appointments Plugin | — | Update simply-schedule-appointments plugin to version 1.6.11.7, or a newer patched version | May 27, 2026 | May 26, 2026 |
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