Update: Microsoft releases critical Internet Explorer patch

IDG News Service - Microsoft Corp. has released its security software patches for April, addressing an unpatched bug in the Internet Explorer browser that hackers had been exploiting for several weeks.

As expected, the company released five patches, called "updates" in Microsoft parlance, addressing a number of critical vulnerabilities in IE and the Windows operating system. Microsoft also released an update for Outlook Express, rated "important," and a fix for Windows FrontPage Server Extensions and SharePoint Team Services 2002, rated "moderate."

In Microsoft's rating system, the most serious vulnerabilities are rated "critical," meaning they could allow unauthorized software to be installed without user action. The "critical" designation is followed by "important," and then "moderate" ratings.

The most anticipated of this month's update is the MS06-013 patch, which fixes several IE bugs, including the "create TextRange ()" vulnerability reported last month. Hackers had been exploiting this problem by installing unauthorized software on PCs by tricking users into visiting sites that took advantage of the bug.

The problem was serious enough that security vendors eEye Digital Security Inc. and Determina Inc. created patches to address it. On Tuesday, eEye said that it had seen more than 156,000 downloads of its software, which Microsoft does not recommend.

Because of this vulnerability, Isabel Maldonado ended up following Microsoft's advice and disabling Active Scripting on the 1,100 workstations she administers at the county attorney's office in Maricopa, Arizona. Her office's support desk ended up fielding about 100 support calls as a result of these changes over the two-week period that the flaw remained unpatched, said Maldonado, a LAN (local area network) administrator with the county.

Microsoft has said that it tends to avoid releasing early patches -- even when they relate to "0day" bugs that hackers are already exploiting -- because customers find the regular monthly patch releases far less disruptive.

But Maldonado said she would have been happy to have the TextRange () problem patched earlier. "I would have much rather they'd rushed out a patch," she said. "I can't think of a customer that would say, 'Oh no. Don't send me the patch right now,' if there's a 0day alert."

Security researchers had reported four separate IE vulnerabilities prior to the release of the MS06-13 update, but Microsoft said it has addressed a total of 10 issues -- including address spoofing and cross-site scripting vulnerabilities -- with the patch.

The IE update also will include changes to the way that IE handles ActiveX controls, meaning that on some Web sites, users may now have to click through some extra steps when using dynamic content like Flash animation. These changes come as the result of a $521 million judgment against Microsoft in a patent lawsuit brought by Eolas Technologies Inc. and the University of California.