CVE-2017-20206

CRITICAL EXPLOITED

Appointments plugin for WordPress <=2.2.1 - Code Injection

Title source: llm

Description

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.

References (3)

[Patch] https://plugins.trac.wordpress.org/changeset/1733186/appointments

[Press/Media Coverage, Third Party Advisory] https://www.wordfence.com/blog/2017/10/3-zero-day-plugin-vulnerabilities-exploited-wild/

[Third Party Advisory] https://www.wordfence.com/threat-intel/vulnerabilities/id/7e8f230e-3f96-4efd-806d-72725b960303?source=cve

Scores

CVSS v3 9.8

EPSS 0.0033

EPSS Percentile 55.8%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation Intel

VulnCheck KEV 2017-10-02

Classification

CWE

CWE-502

Status published

Affected Products (1)

wpmudev/appointments < 2.2.1

Timeline

Published Oct 18, 2025

Tracked Since Feb 18, 2026