Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder 5.1.16 - 6.1.1 - Authenticated (Subscriber+) PHP Object Injection To Arbitrary File Read

The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to PHP Object Injection in versions 5.1.16 to 6.1.1 via deserialization of untrusted input in the parseUserProperties function. This makes it possible for authenticated attackers, with Subscriber-level access and above, to inject a PHP Object. The additional presence of a POP chain allows attackers to read arbitrary files. If allow_url_include is enabled on the server, remote code execution is possible. While the vendor patched this issue in version 6.1.0, the patch caused a fatal error in the vulnerable code, due to a missing class import, so we consider 6.1.2 to be the most complete and best patched version.

An attacker needs Subscriber access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Fluent Forms 6.1.2 closes this, and updating the plugin is the step that ends it.

• Firewall
• Scanner
• Alerts