Microsoft issues out-of-band security bulletin and patch today August 2, 2010.  Out of band means released ahead of the regular scheduled monthly update.  The out-of-band patch is designed to address a security flaw in the way shortcuts are displayed.

Software affected includes Windows operating system, various versions, and is rated critical. Microsoft encourages users to take action

This security update is rated Critical for all supported editions of Microsoft Windows listed here and obtained from Microsoft

Operating System
Windows XP Service Pack 3
Windows XP Professional x64 Edition Service Pack 2
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Server 2003 with SP2 for Itanium-based Systems
Windows Vista Service Pack 1 and Windows Vista Service Pack 2
Windows Vista x64 Edition Service Pack 1 and Windows Vista x64 Edition Service Pack 2
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2
Windows 7 for 32-bit Systems
Windows 7 for x64-based Systems
Windows Server 2008 R2 for x64-based Systems*
Windows Server 2008 R2 for Itanium-based Systems

Recommendation from Microsoft.  Customers who have not enabled automatic updating need to check for updates and install this update manually.

Microsoft Security Advisory