Microsoft released an emergency IE patch on Tuesday after deciding that an upswing in hacking attacks targeting a zero-day vulnerability in IE 6 and 7 couldn't wait for the next scheduled edition of Patch Tuesday, due on 13 April.
The cumulative IE update (MS10-018) also fixes nine other security bugs in Microsoft's browser software. All versions of IE from 5.01 to 8.0, on client and servers, are vulnerable to varying degrees and need patching.
The zero-day vuln involves the iepeers.dll library and creates a handy mechanism to drop malware onto vulnerable systems. Other flaws fixed by the release focus on memory corruption vulnerabilities, as explained by the SANS Institute's Internet Storm Centre here.
The release marks the second time in the first three months of 2010 that Redmond has been obliged to release an out-of-band patch to address critical vulnerabilities in Internet Explorer.
Andrew Storms, director of security operations for network security firm nCircle, commented: "All users should install this new patch immediately, and if you haven't already upgraded to IE8, now is a very good time to seriously consider it."
Microsoft's fix came little over three weeks after it publicly confirmed the flaw. A patch development time of two months or more is much more common.
"The security community has been wondering how Microsoft was able to release this update so quickly, and the answer is that the bug was responsibly disclosed to them before it became public,” Storms explained. ®