Unserialization vulnerability in Relevanssi Premium could allow admins to execute arbitrary code (in some circumstances)

Score Vector Complexity Authentication Confidentiality Integrity Availability
9
High
Network Low Single Complete Complete Complete

You can read more about CVSS base scores on Wikipedia or in the CVSS specification.

Vulnerability

If logged in as an admin on any site you can go to settings, Relevanssi Premium, import or export options. This is a text field that accepts a serialised PHP object. It is possible to submit a string that contains an evil encoded object that executes arbitrary code (if there are classes available with particular methods such as __destruct).

Proof of concept

Achieving arbitrary code execution depends on which classes are available (i.e. which plugins and themes are installed and active). It won’t be possible in all situations.

Mitigation/further actions

Upgrade to version 1.14.6.1 or later.