Update: Microsoft has released an official patch. Uninstall Ilfak's and install Microsoft's if it was not installed via Automatic Updates.
Security Now! Notes for Episode #20
Anyone that runs Windows and uses any web browser is seriously encouraged to install Ilfak Guilfanov’s patch as found on either his blog, or Steve Gibson’s Security Now! Show Notes page. This is a vital patch to be used until Microsoft releases an official patch.
This current exploint is very serious and is being used by malicious websites to download and install all many of Spyware, Adware and other Malware.
Please install this patch ASAP.
[Note: This patch does not work on any versions of Windows prior to Windows 2000. Users of Windows from version 3.1 to Windows Me (including 98, 98se) are vulnerable to this flaw but there has been no announce fix. As these products are no longer supported, it is likley a fix for these version will not be made available by Microsoft. If using these versions of Windows, it is strongly advised not to visit unknown websites. ]