Microsoft Windows Logon Screensaver Local Privilege Escalation Vulnerability

QUOTE
The Microsoft Windows default logon screensaver is reported prone to a local privilege escalation vulnerability. It is reported that the screensaver is started with SYSTEM privileges on Microsoft Windows NT, 2000 and XP computers.

A local attacker that has sufficient privileges to modify or replace the default logon screensaver, or that had sufficient privileges to modify registry entries that relate to the logon screensaver, may exploit this vulnerability to attain local SYSTEM privileges. The default configuration for the software may expose this vulnerability on affected platforms due to lax permissions on the screensaver executable. This could vary depending on the host platform.

http://www.securityfocus.com/bid/11711/discussion/