The Simply Schedule Appointments plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 1.6.12.32 via the 'recursive' parameter. This makes it possible for unauthenticated attackers to extract customer PII — including names, email addresses, phone numbers, and custom form field data — stored in appointment records, as well as per-appointment publictoken values. The leaked per-appointment publictoken values also enable unauthenticated attackers to delete arbitrary appointments via the DELETE /wp-json/ssa/v1/appointments/{id} endpoint, which accepts the token as sole authorization.

The Simply Schedule Appointments plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.6.12.31 via the 'completegroup' parameter due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with subscriber-level access and above, to disclose every co-booker's private per-appointment idtoken (exposed as publictoken) alongside their PII (name and email address), then use each leaked token to read, overwrite arbitrary appointment meta on, or cancel the co-booker's appointment via the same REST controller. Exploitation requires the attacker to possess a valid idtoken for any single appointment within the targeted group booking.

The Simply Schedule Appointments plugin for WordPress is vulnerable to Local File Inclusion in all versions up to, and including, 1.6.12.27 via the 'ssalocale' parameter parameter. This makes it possible for authenticated attackers, with subscriber-level access and above, to include and execute arbitrary .php files on the server, allowing the execution of any PHP code in those files. This can be used to bypass access controls, obtain sensitive data, or achieve code execution in cases where .php file types can be uploaded and included. Notably, exploitation does not require authentication in practice, as the locale filter is installed unconditionally on every request during pluginsloaded and the callback performs no nonce or capability check before returning the raw GET parameter value.

Unauthenticated Insecure Direct Object References (IDOR) in Simply Schedule Appointments <= 1.6.12.31 versions.

Unauthenticated Broken Access Control in Simply Schedule Appointments <= 1.6.12.29 versions.

Unauthenticated Cross Site Scripting (XSS) in Simply Schedule Appointments <= 1.6.10.6 versions.