From:
http://www.vbulletin.com/forum/showthread.php?t=91409
vBulletin 2.3.4
vBulletin 2.3.4 is a security and bug fix release. We recommend you upgrade as soon as possible; if this is not possible, you can simply use the updated calendar.php from this version to obtain the security fix.
Files Changes (from 2.3.3)
Main Directory: calendar.php, member.php, member2.php, report.php
Admin Directory: bbimport.php, functions.php, index.php
Mod Directory: none
The usuals (for version numbers): admin/global.php, admin/install.php, admin/upgrade1.php