As expected, Microsoft yesterday released its security fixes for January. This time around, there are two bulletins, which address three distinct security flaws. One bulletin, MS11-001, applies only to Windows Vista. The other, MS11-002, applies to all supported versions of Windows, and is rated Critical for most. More detailed information, and download links for the installation packages, are in the Security Bulletin Summary for January. Both patches are likely to require a reboot.
As usual, I recommend that you install these updates as soon as you conveniently can.