CVE-2026-116866 in Extra Fees Plugin
Summary
by MITRE • 10/29/2026
Contributor PHP Object Injection in Extra Fees Plugin for WooCommerce <= 4.4.0 versions.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified as Contributor PHP Object Injection within the Extra Fees plugin for WooCommerce, affecting versions up to and including 4.4.0, represents a critical security flaw rooted in improper input validation and unsafe deserialization practices. This type of vulnerability allows an attacker with contributor-level or lower privileges on a WordPress installation to manipulate serialized data structures that are subsequently passed to PHP's unserialize function without adequate sanitization. In the context of web applications like WooCommerce, which handle sensitive e-commerce transactions and user data, such flaws can lead to severe compromises of system integrity and confidentiality. The root cause typically lies in the plugin’s handling of form submissions or AJAX requests where user-supplied input is directly incorporated into a serialization process without verifying its origin or structure, thereby enabling an attacker to craft malicious payloads that exploit internal application logic.
From a technical perspective, PHP Object Injection occurs when untrusted data influences the creation or modification of objects within the application's runtime environment. When these manipulated objects are later deserialized by the framework or plugin code, they can trigger unintended side effects such as arbitrary file reads, remote code execution, or denial of service conditions depending on which classes and methods are available in the global scope. In WordPress environments, this is particularly dangerous because many core files and third-party plugins define magic methods like __wakeup(), __destruct(), or __toString() that execute automatically during deserialization. An attacker can leverage these entry points to chain together existing library functions into a gadget chain, effectively bypassing standard authentication mechanisms since the exploit requires only contributor-level access rather than administrator privileges. This lowers the barrier for exploitation significantly, as many e-commerce sites grant contributors permissions to manage products or orders without full administrative control.
The operational impact of this vulnerability is substantial, potentially allowing attackers to gain unauthorized access to sensitive customer information including names, addresses, and payment details stored in the WooCommerce database. Furthermore, successful exploitation could lead to complete site takeover if the attacker can escalate privileges through file inclusion attacks or by modifying configuration files that dictate application behavior. This compromises not only the immediate security of the website but also erodes trust among customers who expect their financial data to be protected under strict compliance standards such as PCI DSS. Additionally, compromised sites may be used for further malicious activities including phishing campaigns, malware distribution, or botnet recruitment, thereby affecting downstream users and potentially leading to blacklisting by search engines and security vendors.
To mitigate this risk, immediate action is required to update the Extra Fees plugin to a version greater than 4.4.0 where these vulnerabilities have been addressed through improved input validation and secure deserialization patterns. Administrators should also review user roles within their WordPress installation ensuring that only trusted individuals are assigned contributor or higher privileges. Implementing Web Application Firewalls can provide an additional layer of defense by detecting and blocking known exploitation attempts related to PHP object injection. Regular security audits using static analysis tools configured to detect unsafe function calls like unserialize() with dynamic inputs will help identify similar weaknesses across the codebase before they can be exploited in production environments. Adhering to secure coding guidelines such as those outlined in CWE-502 for Deserialization of Untrusted Data and referencing MITRE ATT&CK techniques related to privilege escalation via injection attacks ensures a robust defense posture against this class of vulnerabilities.