---
id: CVE-2026-91109
title: >-
  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…
summary: >-
  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…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-639
vendor: croixhaug
product: Simply Schedule Appointments
affected:
  - simply_schedule_appointments <= 1.6.12.31
published: '2026-10-01'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T04:18:21.557'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-91109'
references:
  - url: >-
      https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L1966
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L2315
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-appointment-model.php#L3160
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.27/includes/class-db-model.php#L348
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset/3709365/simply-schedule-appointments/trunk/includes/class-appointment-model.php
    label: security@wordfence.com
  - url: >-
      https://www.wordfence.com/threat-intel/vulnerabilities/id/d1cd3de2-16ca-4f95-ad6f-47cfbe00c959?source=cve
    label: security@wordfence.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-01T03:36:04.808Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.