Microsoft has published an out-of-band security bulletin--MS12-063--to address a vulnerability that is being actively exploited in attacks in the wild. In addition, Microsoft also released an update to resolve a critical flaw in Adobe Flash in Internet Explorer 10--which is the default browser in Windows 8 and Windows Server 2012.
Microsoft has responded quickly in its investigation of reports that a zero-day vulnerability in Internet Explorer is being actively exploited. Microsoft issued a security advisory with workarounds, and mitigating factors to help customers guard against attacks pending a fix. Then, it released a one-click Fix-It tool to protect customers while kicking its developers in to high gear to create a more permanent fix.
Andrew Storms, director of security operations for nCircle, praised Microsoft's quick turnaround, but he also feels there is more on the line than just protecting customers from attacks. "Microsoft had to respond very quickly to this bug. In addition to the serious security threats it posed to their customers, Internet Explorer's market share is at risk. Many security pundits and organizations have been telling users to switch browsers until a patch is available. I'm sure that got the attention of a lot of Microsoft executives."
To Microsoft's credit, this is the first "zero-day" to hit Internet Explorer in nearly two years. It seems like it was once a much more common occurrence, and that once upon a time Microsoft wasn't this good at cranking out the fix. Microsoft has come a long way in improving its own response to identified security issues, and in setting the bar for other software vendors to strive for.
Separate from the MS12-063 patch, which applies to Internet Explorer 7, 8, and 9, Microsoft also addressed a critical security issue in Internet Explorer 10. There are updates available for both 32-bit and 64-bit Windows 8, and for Windows Server 2012 to fix issues in Adobe Flash code embedded in Internet Explorer 10.
In previous versions of Internet Explorer, Adobe Flash is treated as a separate, standalone application. That software is updated by Adobe, and the patch is traditionally applied outside of the Windows Update or Microsoft Patch Tuesday processes. However, because Flash is now embedded in Internet Explorer 10, the burden falls on Microsoft to develop and release the appropriate patch.
If you have Automatic Updates enabled, you don't need to do anything. However, if you don't have Automatic Updates enabled, you should download and apply these updates as soon as possible.