CVE-2026-15962 in Fluent Forms Pro Add On Pack Plugin
Summary
by MITRE • 07/26/2026
The Fluent Forms Pro Add On Pack plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 6.2.6 via deserialization of untrusted input. 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 change user passwords and potentially take over administrator accounts. Note: This can only be exploited if user update integration is enabled and a user meta field is mapped.
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Analysis
by VulDB Data Team • 07/26/2026
The Fluent Forms Pro Add On Pack plugin for WordPress presents a critical security vulnerability classified as PHP Object Injection affecting versions up to and including 6.2.6. This vulnerability stems from improper handling of untrusted input during the deserialization process, creating a pathway for malicious exploitation that aligns with CWE-502, which specifically addresses unsafe deserialization of untrusted data. The flaw is particularly concerning because it requires only subscriber-level access or higher to exploit, making it accessible to users who already have some level of system permissions.
The technical implementation of this vulnerability occurs when the plugin processes user input that contains serialized PHP objects without adequate sanitization or validation. When an authenticated attacker with subscriber privileges or above submits maliciously crafted data through the plugin's form handling mechanisms, the system attempts to deserialize this untrusted input, executing arbitrary PHP code in the process. This deserialization flaw creates a dangerous attack surface where attackers can inject malicious objects that execute code on the target server with the privileges of the web application.
The operational impact of this vulnerability extends beyond simple code execution, as it includes the potential for complete account takeovers when combined with a POP (Property Oriented Programming) chain. The presence of a working POP chain enables attackers to manipulate user metadata and password fields within the WordPress system, allowing them to change administrator passwords and gain full administrative control over the affected website. This exploitation pathway represents a significant threat to WordPress site security, particularly given that the vulnerability requires minimal privileges to exploit and can lead to complete system compromise.
The specific conditions required for successful exploitation include having user update integration enabled within the plugin configuration and ensuring that at least one user meta field is mapped within the system. These prerequisites mean that not all installations are equally vulnerable, but they also indicate that the risk exists in any properly configured environment where these features are active. This vulnerability demonstrates how seemingly minor configuration options can create significant security risks when combined with improper input validation mechanisms.
Security mitigations for this vulnerability should focus on immediate patching of the affected plugin to version 6.2.7 or later, which contains the necessary fixes for the deserialization flaw. Organizations should also implement strict input validation and sanitization measures for all user-submitted data, particularly when processing serialized objects. Additionally, administrators should review and disable unnecessary user update integration features where possible, and monitor user meta field mappings to reduce potential attack vectors.
The vulnerability aligns with ATT&CK technique T1059.007 for PHP code execution and T1531 for credential access through password modification. It represents a classic example of how authentication bypasses can be achieved through privilege escalation within web applications, and it highlights the importance of secure coding practices around object serialization in PHP applications. This vulnerability serves as a reminder that even plugins with legitimate business functions can introduce critical security risks when proper input validation and sanitization controls are not implemented.
Organizations should also consider implementing network-level protections such as web application firewalls to detect and block suspicious deserialization patterns, while maintaining regular security audits of all installed WordPress plugins. The vulnerability demonstrates the necessity of comprehensive security testing including dynamic analysis for serialization-related issues, particularly in environments where user input is processed through complex plugin ecosystems. Proper security monitoring should include detection of unusual user metadata modifications and password change activities that could indicate exploitation attempts.