WordPress security changelog
MEDIUM CVE-2026-91109 Received

Simply Schedule Appointments: Broken access control

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 makes it possible for authenticated attackers, with subscriber-level access and above, to disclose every co-booker's private per-appointment id_token (exposed as public_token) 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 id_token for any single appointment within the targeted group booking.

CVE / CNA score 6.5 CVSS 3.1 · security@wordfence.com
NVD score Pending NVD has not published its own CVSS assessment.
Component
Simply Schedule Appointments
Plugin slug
simply-schedule-appointments
Affected
<= 1.6.12.31
Safe version
See mitigation notes
Published
Oct 01, 2026
Weakness
CWE-639 — Authorization Bypass Through User-Controlled Key

This CVE was published Oct 01, 2026 and is one of 43 known issues for this plugin.

What to do

Update, patch or deactivate.

No confirmed fixed release is identified. Disable the affected feature or deactivate the component until an upstream fix is confirmed. Upstream 1.6.12.33 is available and may resolve this issue, but its changelog does not clearly establish a matching fix; it is not marked safe here. Authorize each co-booker record independently of group membership and omit their tokens and private details from group responses.

No confirmed safe version is listed. Consider a vendor-supported patch or temporarily restricting the affected functionality while you assess the risk.

Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.

Source record

Technical description

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 makes it possible for authenticated attackers, with subscriber-level access and above, to disclose every co-booker's private per-appointment id_token (exposed as public_token) 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 id_token for any single appointment within the targeted group booking.

CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References

Primary and upstream sources