Recently IE has had a zero-day exploit reported for all versions of IE except version 10 in Windows 8.
Microsoft has issued an emergency fix-it for this exploit just recently (about three hours ago) that is a temporary workaround until the needed critical update is deployed on Friday September 21st, 2012 at around 10 PM PST time by Microsoft. Exploit involves visiting a malicious website and then a Trojan Poison Ivy is downloaded and installed on the victim’s computer using the zero-day vulnerability noted above and in the links to follow.
NOTE: This zero-day only affects IE, it does not affect Firefox or Chrome according to the latest information available.
http://blogs.technet.com/b/msrc/ This link includes a direct link to the fix-it files needed to enable and disable the fix.
More details about this action can be found here: http://news.cnet.com/8301-1009_3-57516392-83/microsoft-issues-fix-for-ie-hole-full-update-coming-friday/
Users who do not apply this fix-it workaround are strongly advised to not use IE until Microsoft issues the critical update for IE on Friday.