CVE-2026-13358: Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin <= 1.6.12.10 - Authenticated (Contributor+) Insecure Direct Object Reference to Sensitive Information Exposure

The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.6.12.10 via the ssapastappointments due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with contributor-level access and above, to access appointment records belonging to arbitrary users and harvest the per-appointment ownership tokens (32-character hashes) embedded in the rendered HTML, which can then be used without any authentication to read or modify those appointments including full customer PII such as name, email, phone number, and private notes. The /wp-json/ssa/v1/render-shortcode REST endpoint is registered unconditionally on restapiinit regardless of whether the Divi theme is installed, and its permission callback only requires currentusercan('editposts'), meaning any Contributor-level account is sufficient to trigger this entire exploit chain.