Deserialization in Wpmudev Appointments
CVE-2017-20206
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.
Vulnerability class: Insecure Deserialization
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (52.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 52.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: +0.000
Affected products
- Wpmudev Appointments — versions 0
Weakness classification (CWE)
References
- www.wordfence.com/threat-intel/vulnerabilities/id/7e8f230e-3f96-4efd-806d-72725… (Third Party Advisory)
- www.wordfence.com/blog/2017/10/3-zero-day-plugin-vulnerabilities-exploited-wild/ (Third Party Advisory, Press/Media Coverage)
- plugins.trac.wordpress.org/changeset/1733186/appointments (Patch)
Frequently asked questions
- What is CVE-2017-20206?
- CVE-2017-20206 is a critical-severity vulnerability in Wpmudev Appointments, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2025-10-18.
- How severe is CVE-2017-20206?
- Critical severity. CVSS v3 base score is 9.8 out of 10.