Description

The User Frontend WordPress plugin before 4.3.11 does not prevent user-supplied field values from being deserialized when a submitted post is reopened in its frontend editing form, allowing authenticated users with subscriber-level access and above to perform PHP Object Injection, which may lead to remote code execution when a suitable gadget chain is present on the site.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T06:17:16.643Z",
  "pubdate": "2026-09-02T06:17:16.643Z",
  "executiveSummary": "The User Frontend WordPress plugin is susceptible to a PHP Object Injection vulnerability due to improper input handling during frontend post-editing processes. This flaw allows an authenticated user with subscriber-level permissions or higher to supply malicious serialized data to the application, which is subsequently deserialized without validation.\nThe vulnerability resides in how the plugin handles user-supplied field values when a post is reopened in the frontend editing interface. By injecting a crafted serialized object, an attacker can manipulate the application state, trigger arbitrary code execution, or perform other unintended actions, provided a viable POP (Property Oriented Programming) gadget chain exists within the WordPress environment.\nSuccessful exploitation requires the attacker to have at least subscriber-level authenticated access to the target WordPress site. The impact of this vulnerability is critical, as it can lead to full remote code execution, unauthorized data modification, or complete system compromise, depending on the available gadget chains present in the application's codebase or active plugins.\nThis vulnerability affects all versions of the User Frontend plugin prior to version 4.3.11.",
  "technicalDetails": "The root cause of this vulnerability is the unsafe deserialization of user-controlled input. The User Frontend plugin fails to implement adequate sanitization or verification mechanisms when processing field values during the frontend post editing lifecycle. Specifically, when an existing post is retrieved for modification, the plugin processes serialized metadata that was stored previously. If this metadata is manipulated by an attacker, the underlying PHP unserialize() function processes the malicious input.\nThe attack flow begins when an authenticated subscriber identifies a field within the frontend editing form that interacts with serialized data. The attacker intercepts the HTTP request and replaces the legitimate field value with a malicious PHP serialized string. When the server-side component of the User Frontend plugin processes this submission, it invokes the unserialize() function on the tainted data.\nPHP Object Injection occurs when an attacker passes a serialized object that, upon being instantiated by the application, triggers its magic methods (e.g., __destruct(), __wakeup(), or __toString()). If the application's runtime environment—including the WordPress core, the plugin itself, or other installed plugins—contains classes that perform sensitive operations (such as file system interactions, database queries, or command execution) within these magic methods, an attacker can chain these objects together to form a POP chain. This chain is used to achieve Remote Code Execution (RCE).\nBecause the vulnerability triggers during the post-editing workflow, the attacker must be authenticated as a registered user (subscriber level or higher). The vulnerability is present in the plugin's core logic responsible for rendering and processing frontend forms. Since PHP's unserialize() is inherently dangerous when applied to untrusted input, the lack of input validation or the use of safer data interchange formats (such as JSON) allows the injected payload to be processed as a valid object structure. The post-exploitation impact is severe, potentially granting the attacker arbitrary code execution with the permissions of the web server user, leading to full site compromise, lateral movement within the server environment, and potential exfiltration of sensitive configuration data or credentials stored in the WordPress database."
}