CVE-2017-20206: Wpmudev Appointments

Critical severity, CVSS 9.8. EPSS: 0.7% chance of exploitation in the next 30 days.

The Appointments plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 2.2.1 via deserialization of untrusted input from the `wpmudev_appointments` cookie. This allows unauthenticated attackers to inject a PHP Object. Attackers were actively exploiting this vulnerability with the WP_Theme() class to create backdoors.

Affected products

• Wpmudev Appointments: up to and including 2.2.1

Published 2025-10-18. Last modified 2026-06-17.