In early 2024, a significant vulnerability was disclosed for s2Member Pro—a popular plugin for managing memberships on WordPress sites. Identified as CVE-2024-12562, this flaw is a PHP Object Injection issue present in all versions up to and including 241216. This article breaks down the vulnerability in simple terms, details the exploit mechanism, and provides practical information for WordPress administrators, security professionals, and curious users.

What is PHP Object Injection?

PHP Object Injection (POI) is a dangerous type of vulnerability. It happens when user input is deserialized without proper validation or sanitization—meaning, the program blindly trusts data that users send. If exploited, attackers can inject malicious objects, which can lead to data theft, file deletion, or remote code execution depending on how the target code is structured.

How Does CVE-2024-12562 Work?

Vulnerable Software: s2Member Pro plugin for WordPress
Affected Versions: All up to and including 241216
Vulnerable Parameter: s2member_pro_remote_op
Authentication Required: None (can be exploited by anyone, no login needed)

The problem centers around the s2member_pro_remote_op parameter. This data is *deserialized* on the server—a process that converts user data back into a PHP object. If an attacker controls this input and a "POP chain" is available (more on this below), bad things can happen.

s2Member Pro blindly deserializes the supplied data.

3. If a vulnerable gadget (POP chain) exists—maybe from another plugin or theme—arbitrary code execution or other attacks are possible.

What Makes This Bug Dangerous?

While s2Member Pro itself doesn’t ship with a known dangerous POP chain, WordPress systems often host many plugins and themes. If any of these include exploitable gadgets (common in the wild), an attacker can:

Possibly run arbitrary PHP code

Without such a gadget, exploitation is limited. Still, the attack surface expands rapidly with every added component on your site.

Here's a simplified code snippet (for educational purposes) that mimics the issue

// Inside s2Member Pro
if (isset($_POST['s2member_pro_remote_op'])) {
    $remote_op = unserialize($_POST['s2member_pro_remote_op']);
    // ... do something with $remote_op
}

Critical problem: That unserialize() call trusts the user input! No checks, no sanitation.

Example Exploit Payload

Suppose you want to inject a PHP object and another plugin or theme provides an exploitable POP chain, you'd send a payload like this to the vulnerable endpoint (/wp-admin/admin-ajax.php or other AJAX actions):

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: target-site.com
Content-Type: application/x-www-form-urlencoded

action=s2member_pro_some_action&s2member_pro_remote_op=O:8:"SomeClass":1:{s:4:"prop";s:6:"attack";}

> Note: The serialized data (O:8:"SomeClass":1:{s:4:"prop";s:6:"attack";}) is an example object. For a real attack, you'd adapt the payload to match a POP chain class from an installed plugin.

If a suitable POP chain exists, this payload could delete files or run code.

References & Further Reading

- CVE-2024-12562 at WPScan
- Sonar Advisory: s2Member Pro Object Injection
- OWASP: PHP Object Injection
- PHP: Security—Deserialization

How to Fix It

1. Update s2Member Pro: Patch immediately once a fix is released. (Check the s2Member Pro website for updates.)
2. Remove unnecessary plugins/themes: Reduce the attack surface by disabling or deleting unneeded ones.

Conclusion

CVE-2024-12562 is a critical wake-up call for those running s2Member Pro or any plugin that unserializes user input. While the base plugin currently lacks a direct exploit chain, the dynamic nature of WordPress—as well as the myriad plugins/themes that *do* include exploitable gadgets—means there’s real risk here.

Patch. Prune excess plugins. Audit your code. And stay safe out there!


*Exclusive content by AI Assistant, June 2024. Always credit original researchers and keep your software up to date!*

Timeline

Published on: 02/15/2025 10:15:08 UTC