CVE-2026-59523

Unauthenticated Insecure Direct Object References (IDOR) vulnerability in Simply Schedule Appointments up to version 1.6.12.31.

Simply Schedule Appointments plugin version 1.6.12.29 and earlier contains a Broken Access Control vulnerability that can be exploited without authentication, allowing unauthorized access to functionality.

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 'ssa_locale' 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 plugins_loaded and the callback performs no nonce or capability check before returning the raw GET parameter value.

Unauthenticated SQL Injection vulnerability in Simply Schedule Appointments versions up to 1.6.12.10.

There is an unauthenticated SQL injection vulnerability in Simply Schedule Appointments versions up to 1.6.9.27.

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. Unauthenticated attackers can extract customer PII (names, email addresses, phone numbers, custom form field data) and per-appointment public_token values, which also enables deletion of arbitrary appointments via the DELETE /wp-json/ssa/v1/appointments/{id} endpoint.

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 'complete_group' parameter due to missing validation on a user-controlled key. This allows authenticated attackers with subscriber-level access and above to disclose every co-booker's private id_token and PII, then use each leaked token to read, overwrite arbitrary appointment meta, or cancel the co-booker's appointment.

Unauthenticated CSRF vulnerability in Simply Schedule Appointments versions up to 1.6.12.23. An attacker can exploit this to perform unauthorized actions in the context of a logged-in administrator.

Unauthenticated Cross Site Scripting (XSS) vulnerability in Simply Schedule Appointments plugin up to version 1.6.12.10. An unauthenticated attacker can inject malicious scripts.

The Simply Schedule Appointments WordPress plugin before version 1.6.12.11 does not perform a capability check on an administrative appointment-listing shortcode, and its per-user result scoping fails open for non-staff users. This allows users with the Contributor role and above to disclose all customers' appointment records, including names, email addresses, phone numbers and notes, across the whole site.