vBulletin PHP object injection vulnerability
Description
vBulletin versions 3.5 through 5.x contain a PHP object injection vulnerability that allows attackers to exploit insecure deserialization of user-supplied data. This vulnerability occurs when untrusted data is passed to PHP's unserialize() function without proper validation, enabling attackers to inject arbitrary PHP objects. The vBulletin team has released security patches for all affected versions including 3.8.7, 4.2.2, and all 5.x releases to address this critical security issue.
Remediation
Apply the official security patches immediately for your vBulletin version:
1. Identify your current vBulletin version through the AdminCP
2. Download the appropriate patch from the official vBulletin forum (see references)
3. Back up your vBulletin installation and database before applying patches
4. Upload and apply the patch files according to vBulletin's patch instructions
5. Verify the patch installation by checking the version number in AdminCP
6. If patching is not immediately possible, implement input validation to sanitize all user-supplied data before processing
For custom code, avoid using unserialize() on untrusted data. Instead, use json_decode() for data interchange:
// Insecure - vulnerable to object injection $data = unserialize($_COOKIE['user_data']); // Secure alternative - use JSON for data serialization $data = json_decode($_COOKIE['user_data'], true);