Today Microsoft *finally* patched a security hole found in all of it's versions of IE which was announced on Sunday.
An emergency patch was released yesterday, available to all supported versions of Windows as well was Windows XP; which has expired as of April 8th.
If you have automatic updates turned on, then you will notice a patch available late yesterday or this morning.
Alternatively, you can browse to the Windows Update site and update all available patches.
Given the importance of this update, it's advisable to run this update sooner than later.