Internet Explorer was discovered to have a vulnerability that would allow hackers to gain control of a Windows PC late last month. In order for the exploit to work, users had to be running an older version of the program, versions 6 to 8, specifically, and have visited a malicious website.
Microsoft attempted to remedy the problem with various workarounds and a "one-click fix," all of which are temporary workarounds. Normally, bugs and exploits would have been addressed during Microsoft's normally scheduled Patch Tuesday, though when it didn't come, IT professionals began to wonder when it would.
We now have the answer: today. The patch should be available through Windows Update and marked as 'Critical', meaning it will be automatically installed, as long as the user has Automatic Updates enabled. If you use an older version of Internet Explorer, pre-version 9, you should make sure you install the update, especially if you don't have Automatic Updates enabled.