CVE-2026-9188

MEDIUM
Published Jul 2, 2026 Modified Jul 2, 2026 CWE-639

Description

The Appointment Bookings for Zoom GoogleMeet and more – Wappointment plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to and including 2.7.6 via the `appointmentkey` parameter due to the appointment `edit_key` — the sole authorization token consumed by `tryCancel()` — being generated as a predictable, unsalted MD5 hash of only `client_id` (a sequential integer), `start_at` (a publicly observable appointment timestamp), and `staff_id` (a small enumerable integer), with no secret salt or random component, and the unauthenticated cancellation and rescheduling REST endpoints performing no ownership or identity verification beyond matching this reconstructible key. This makes it possible for unauthenticated attackers to compute valid `edit_key` values for appointments belonging to other users and cancel or reschedule those appointments arbitrarily. Exploitation requires the `allow_cancellation` or `allow_rescheduling` setting to be enabled on the site, both of which are common configurations for active booking deployments; an attacker can obtain the inputs needed to reconstruct a victim's key by booking their own appointment to observe their sequential `client_id` and correlating publicly visible appointment times and enumerable staff identifiers.

CVSS v3.1 Score

5.3
MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0030
Probability of exploitation
0.21%
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/wappointment/tags/2.7.5/app/Models/Client.php#L39 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.5/app/Services/AppointmentNew.php#L190 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.5/app/Services/AppointmentNew.php#L347 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.5/app/Services/AppointmentNew.php#L40 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.6/app/Models/Client.php#L39 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.6/app/Services/AppointmentNew.php#L190 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.6/app/Services/AppointmentNew.php#L347 https://plugins.trac.wordpress.org/browser/wappointment/tags/2.7.6/app/Services/AppointmentNew.php#L40 https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=3546313%40wappointment&new=3546313%40wappointment&sfp_email=&sfph_mail= https://www.wordfence.com/threat-intel/vulnerabilities/id/07069f39-f892-4c19-8e0b-e5e17b1ffb21?source=cve

Frequently Asked Questions

What is CVE-2026-9188? +
The Appointment Bookings for Zoom GoogleMeet and more – Wappointment plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to and including 2.7.6 via the `appointmentkey` parameter due to the appointment `edit_key` — the sole authorization token consumed by `tryCancel()` — being generated as a predictable, unsalted MD5 hash of only `client_id` (a sequential integer), `start_at` (a publicly observable appointment timestamp), and `staff_id` (a small enumerable integer), with no secret salt or random component, and the unauthenticated cancellation and rescheduling REST endpoints performing no ownership or identity verification beyond matching this reconstructible key. This makes it possible for unauthenticated attackers to compute valid `edit_key` values for appointments belonging to other users and cancel or reschedule those appointments arbitrarily. Exploitation requires the `allow_cancellation` or `allow_rescheduling` setting to be enabled on the site, both of which are common configurations for active booking deployments; an attacker can obtain the inputs needed to reconstruct a victim's key by booking their own appointment to observe their sequential `client_id` and correlating publicly visible appointment times and enumerable staff identifiers. It has a CVSS v3.1 base score of 5.3 (MEDIUM).
How severe is CVE-2026-9188? +
CVE-2026-9188 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0030, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2026-9188? +
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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