CVE-2026-91109 (CVSS 6.5)

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.

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CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0032

Probability of exploitation

0.23%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

References

Other References

https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L1966 https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L2315 https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L3160 https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-db-model.php#L348 https://plugins.trac.wordpress.org/changeset/3709365/simply-schedule-appointments/trunk/includes/class-appointment-model.php https://www.wordfence.com/threat-intel/vulnerabilities/id/d1cd3de2-16ca-4f95-ad6f-47cfbe00c959?source=cve

Frequently Asked Questions

What is CVE-2026-91109? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-91109? +

CVE-2026-91109 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0032, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-91109? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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