CVE-2024-13784 in Contact Form
Summary
by MITRE • 08/16/2026
The Contact Form, Survey, Quiz & Popup Form Builder – ARForms plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.8.5 via deserialization of untrusted input from form submissions. This makes it possible for unauthenticated attackers to inject a PHP Object. No known POP chain is present in the vulnerable software, which means this vulnerability has no impact unless another plugin or theme containing a POP chain is installed on the site. If a POP chain is present via an additional plugin or theme installed on the target system, it may allow the attacker to perform actions like delete arbitrary files, retrieve sensitive data, or execute code depending on the POP chain present.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/16/2026
The ARForms WordPress plugin, specifically versions up through 1.8.5, contains a critical PHP Object Injection vulnerability stemming from the insecure deserialization of untrusted input submitted via its contact forms, surveys, quizzes, and popup builders. This flaw allows any user with access to the public-facing form endpoints to manipulate the internal state of the application by injecting serialized PHP objects into the request payload. The root cause lies in the plugin's failure to validate or sanitize data before passing it to PHP's unserialize function, a common anti-pattern that violates secure coding standards regarding input handling and trust boundaries.
From a technical perspective, this vulnerability is classified under CWE-502, which denotes Deserialization of Untrusted Data. The attacker crafts a malicious serialized object containing specific class instances and method calls, then submits it through the vulnerable form fields. Because WordPress plugins often share global state or have access to sensitive APIs, an injected object can trigger unintended side effects within the application environment if the targeted classes are available in the memory space of the running PHP process.
It is crucial to note that this vulnerability alone does not result in direct remote code execution or system compromise because no Proof-of-Concept POP chain exists within the ARForms plugin itself. A POP chain requires a sequence of gadget methods that, when executed sequentially, lead to arbitrary function calls such as file deletion or command execution. Without these specific gadgets present in the vulnerable software, the injected object remains inert and cannot be exploited for immediate impact.
However, the risk profile changes significantly if the target WordPress installation includes other plugins or themes that contain exploitable POP chains. In such an environment, the ARForms vulnerability serves as a powerful entry point to trigger those external gadget chains. This scenario aligns with ATT&CK technique T1059, Command and Scripting Interpreter, particularly when considering how attackers leverage existing software components to achieve their objectives without writing custom exploit code for every target component.
If an exploitable POP chain is present in another installed plugin or theme, the operational impact can be severe. Attackers may utilize this vector to delete arbitrary files on the server, potentially disrupting service availability or removing security logs. They could also retrieve sensitive data by triggering methods that expose database credentials or user information. In more complex scenarios involving specific gadget chains, it is possible for attackers to achieve Remote Code Execution, effectively taking full control of the web server and gaining access to all hosted applications and databases on that instance.
To mitigate this vulnerability, site administrators should immediately update the ARForms plugin to version 1.8.6 or later, where the deserialization issue has been addressed by implementing strict input validation and whitelisting allowed data types. For sites running older versions that cannot be updated due to compatibility constraints, it is advisable to disable the affected form modules if they are not in use. Additionally, administrators should audit installed plugins for known vulnerabilities involving insecure deserialization and remove any unnecessary or outdated components to reduce the attack surface and eliminate potential POP chains that could be leveraged by this specific entry point.