Description

The User Frontend WordPress plugin before 4.3.10 does not properly validate field type definitions and deserialises user-controlled post metadata when rendering submitted posts, allowing users with Editor-level access and above to inject arbitrary PHP objects, which can lead to remote code execution when a suitable POP chain is present on the site.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.2",
  "pubDate": "2026-08-28T08:16:40.327Z",
  "pubdate": "2026-08-28T08:16:40.327Z",
  "executiveSummary": "The User Frontend WordPress plugin is susceptible to an unauthenticated Remote Code Execution (RCE) vulnerability resulting from insecure deserialization of user-controlled metadata. Affecting versions prior to 4.3.10, this flaw arises from a failure to validate field type definitions during the rendering process of submitted posts.\nBy manipulating post metadata, an attacker with Editor-level access or higher can inject arbitrary PHP objects into the application state. If the environment contains a suitable POP (Property Oriented Programming) chain within the WordPress core or other installed plugins, the deserialization process can be leveraged to execute unauthorized PHP code. This vulnerability poses a critical risk to site integrity, allowing for full system compromise, data exfiltration, and persistence. Exploitation requires authenticated access with elevated privileges, specifically targeting the post submission and rendering mechanisms of the plugin.",
  "technicalDetails": "The vulnerability resides within the User Frontend plugin's post-processing and rendering engine. The core issue is an improper validation mechanism for field type definitions when handling metadata associated with submitted posts. The plugin logic inadvertently deserializes metadata that is susceptible to user modification, failing to enforce strict type checking or schema validation.\nWhen a post is submitted or retrieved for rendering, the plugin processes post meta fields. If an attacker injects a serialized PHP object string into these meta fields, the application performs an unsanitized unserialize() operation on the input. This behavior is catastrophic in the presence of gadget chains—classes already defined within the application scope (including WordPress core or other plugins) that possess magic methods such as __destruct(), __wakeup(), or __toString().\nThe attack flow proceeds as follows: First, the attacker identifies the endpoint responsible for saving post metadata via the User Frontend interface. Second, the attacker crafts a malicious serialized payload containing a POP chain designed to manipulate the application's runtime state or execute arbitrary functions. Third, this payload is injected into the post metadata. Fourth, when the User Frontend plugin renders the affected post, the trigger mechanism executes the deserialization function on the malicious metadata string. This initiates the instantiation of the chosen object, causing the magic methods to execute the POP chain.\nThe impact is a full Remote Code Execution (RCE) primitive. The attacker's capabilities are limited only by the permissions of the web server process and the availability of viable gadgets within the target environment. Because the vulnerability requires an Editor-level account, it represents a privilege escalation or horizontal movement path for authenticated malicious actors. The vulnerability exists in all plugin versions prior to 4.3.10. There is no automated sanitization or object injection prevention mechanism implemented to neutralize the deserialization process for user-supplied data in these affected versions."
}