CVE-2017-20206 - CVE House

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Status published Critical CVE-2017-20206

Appointments <= 2.2.1 - Unauthenticated PHP Object Injection

9.8 CVSS

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

Matt Barry

References

More from wpmudev

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Forminator Forms – Contact Form, Payment Form & Custom Form Builder <= 1.45.0 - Authenticated (Administrator+) SQL Injection via `order_by` Parameter

Forminator Forms – Contact Form, Payment Form & Custom Form Builder <= 1.44.2 - Unauthenticated PHP Object Injection (PHAR) Triggered via Administrator Form Submission Deletion

Forminator Forms – Contact Form, Payment Form & Custom Form Builder <= 1.44.2 - Unauthenticated Arbitrary File Deletion Triggered via Administrator Form Submission Deletion

Forminator <= 1.44.1 - Authenticated (Contributor+) Stored DOM-Based Cross-Site Scripting via id and data-size Parameters

Broken Link Checker <= 2.4.4 - Missing Autorization to Authenticated (Subscriber+) Plugin Status Dashboard View

Affected Vendor

wpmudev

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Affected Software

Appointments

Vulnerable Versions:

0

Timeline

Official Publish: October 18th, 2025

Last Modified: April 8th, 2026

Added to House: July 20th, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weaknesses (CWE)

MITRE ATT&CK TTPs

T1190 Exploit Public-Facing Application

T1059 Command and Scripting Interpreter

T1505.003 Web Shell

T1105 Ingress Tool Transfer

Command and Control

T1068 Exploitation for Privilege Escalation

Privilege Escalation