What’s Vulnerable › Vulnerabilities

CVE-2017-20206: Appointments <= 2.2.1 - Unauthenticated PHP Object Injection

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-10-18 · updated 2026-06-17
• Weakness: CWE-502

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.

Affected products

• wpmudev Appointments: through 2.2.1

References

• https://plugins.trac.wordpress.org/changeset/1733186/appointments
• https://www.wordfence.com/blog/2017/10/3-zero-day-plugin-vulnerabilities-exploited-wild/
• https://www.wordfence.com/threat-intel/vulnerabilities/id/7e8f230e-3f96-4efd-806d-72725b960303?source=cve

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