vBulletin is prone to a cross-site scripting vulnerability because the application fails to properly sanitize user-supplied input.
An attacker may leverage this issue to execute arbitrary script code in the browser of an unsuspecting user in the context of the affected site. This may help the attacker steal cookie-based authentication credentials and launch other attacks.
vBulletin 3.7.2 Patch Level 1 and vBulletin 3.6.10 Patch Level 3 are vulnerable; other versions may also be affected.
VBulletin VBulletin 3.7.2 PL1 VBulletin VBulletin 3.6.10 PL3
The vendor has released fixes. Please see the references for more information.