What the vulnerability does
01Description
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
Explanation of Vulnerability in Simple Terms
02Summary
Fluent Forms versions 5.1.16 through 6.1.1 contain a deserialization vulnerability that allows authenticated users to read sensitive data from the site. An attacker with a low-privilege account can craft malicious input to deserialize untrusted data, potentially exposing confidential information. Update to a version newer than 6.1.1 to resolve this issue.
What an attacker can do
03Attacker Capabilities
Read sensitive data from the site by exploiting unsafe deserialization of untrusted input.
Potential impact on your site
04Site Impact
Any authenticated user can access confidential information stored in the form builder or database.
Conditions required to exploit
05Prerequisites
Attacker must have a low-privilege user account on the site; no user interaction required.
Key dates
06Disclosure timeline
September 2, 2025
CVE published
September 3, 2025
Record updated
