Microsoft has released a 26.9MB patch which fixes five vulnerabilities, including the zero day flaw that is cracking Windows systems via the most common versions of Internet Explorer.
The MS12-063 update provides a fix for the flaw, which is in use by hackers against some companies. The patch also has four more flaw-fixes, which have not been spotted in the wild, according to Redmond.
"The majority of customers have automatic updates enabled and will not need to take any action because protections will be downloaded and installed automatically. For those manually updating, we encourage you to apply this update as quickly as possible," said Yunsun Wee, director of Microsoft Trustworthy Computing in a blog post.
The flaw was rated as critical or moderate risk, depending on which browser and operating system you are running, but would allow full remote code execution on systems running IE 7,8 and 9 running Adobe Flash on fully-patched Windows XP, Vista and 7 machines, using malware embedded in a web page.
It was discovered by security researcher Eric Romang on an Italian hacking tools site, but there have been reports that it has been used to distribute the Poison Ivy Trojan by the same group that exploited the Java zero-day flaw found in the last month.
So far the automatic update service appears to be running a little slow, at least in El Reg offices, but a manual search picks up the patch. As well as being a fairly hefty download size, the fix also requires a total restart (Linux users can look smug now.)
Microsoft will hold an hour-long webcast to discuss the flaw and its implications at 1200 PT (2000 UT) on Friday. ®