Microsoft today released its expected bumper crop of security fixes. There are 16 bulletins this month, of which twelve are for Windows and its components, two for Office (including Office for Mac), and two for server software: Office for Web, and Share Point. Every supported version of Windows has at least one bulletin rated Critical. More detail is available in the Security Bulletin Summary for October. (A breakdown of patch severity by Windows version is in my preview post for this month.)
All of these patches should be available from Windows Update; alternatively, there are download links in the Security Bulletin Summary.
The SANS Internet Storm Center has posted their usual monthly summary of the released patches.
I recommend installing these patches as soon as you conveniently can.