Microsoft has just posted their security patch builletin for the month of December. As usual all required patches for your PC can be found on Windows Update. Here's a brief summary of the two patches released this month:
MS05-054: Cumulative Security Update for Internet Explorer (905915)
Critical
Vulnerabilities exist in Internet Explorer, the most severe of these could allow an attacker to take complete control of an affected system.
MS05-055: Vulnerability in Windows Kernel Could Allow Elevation of Privilege (908523)
Important
A vulnerability exists in the Windows Kernel that could allow elevation of privileges on an affected system. An attacker must have valid logon credentials and be able to log on locally to exploit this vulnerability.
View: Neowin Forum Discussion
View: Microsoft Security Bulletin Summary for December | Microsoft Windows Update