Description

Subscriber PHP Object Injection in WP User Frontend <= 4.3.10 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T12:17:12.267Z",
  "pubdate": "2026-09-02T12:17:12.267Z",
  "executiveSummary": "The WP User Frontend plugin for WordPress, in versions 4.3.10 and earlier, is susceptible to a PHP Object Injection vulnerability.\nThis vulnerability is classified as an Insecure Deserialization flaw, which allows authenticated subscribers to instantiate arbitrary PHP objects.\nThe primary risk implication is the potential for Remote Code Execution (RCE) or other malicious actions, depending on the presence of gadget chains within the application environment.\nSuccessful exploitation requires the attacker to be authenticated with at least subscriber-level privileges, as the vulnerable input vector is processed within a context accessible to logged-in users.\nThe impact is significant, as an attacker could potentially manipulate application state, delete files, or execute arbitrary system commands if a viable POP (Property-Oriented Programming) chain exists in the plugin or the underlying WordPress core/theme ecosystem.\nSecurity teams must prioritize updating the plugin to a secured version to prevent unauthorized code execution and complete site compromise.",
  "technicalDetails": "The vulnerability resides in the way the WP User Frontend plugin handles user-supplied data during its processing flow. Specifically, the plugin employs insecure deserialization of serialized PHP objects, which are passed to the unserialize() function without sufficient sanitization or validation.\nIn PHP, the unserialize() function is inherently dangerous when processing user-controlled input because it allows the instantiation of arbitrary classes that are available in the application's current scope. If an attacker can inject a serialized string, they can control the properties of objects and trigger magic methods, such as __destruct(), __wakeup(), or __toString().\nAn authenticated subscriber can craft a malicious serialized payload and transmit it via the vulnerable input vector identified in the plugin's request handling logic. Upon processing this input, the plugin invokes the unserialize() function, triggering the instantiation of the attacker-controlled object.\nThe exploitation flow proceeds as follows: 1) The attacker identifies the vulnerable endpoint within WP User Frontend that consumes serialized data. 2) The attacker researches the application environment, including active themes and installed plugins, to identify useful 'gadget' classes—classes that contain magic methods capable of performing unintended actions when their properties are manipulated. 3) The attacker constructs a serialized POP chain designed to leverage these gadgets. 4) The attacker sends a request containing the serialized payload to the identified endpoint. 5) The server-side unserialization occurs, executing the logic contained within the gadget chain.\nBecause the payload is processed during the server-side request lifecycle, the exploit executes with the privileges of the web server process. This effectively bypasses standard authorization checks, as the vulnerability is triggered by the deserialization logic itself, not the standard WordPress permission system. Post-exploitation impact varies based on the gadget chains available but can range from information disclosure to full server compromise via arbitrary command execution.\nThe vulnerability affects WP User Frontend versions 4.3.10 and below. It is classified under CWE-502: Deserialization of Untrusted Data. The attack is restricted to authenticated users, specifically those with subscriber or higher roles, but the lack of granular input validation makes it a high-severity entry point for further escalation."
}