Researchers: Newest Microsoft IE patch flawed

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By Sam Costello

(IDG) -- A new patch designed to address six serious security vulnerabilities in Microsoft's Internet Explorer doesn't fix all the problems it purports to, according to security researchers.

The patch, which was released late last Wednesday, is designed to fix a cross-site scripting problem and other security and privacy flaws affecting Internet Explorer (IE) versions 5.01 through 6 and the Outlook e-mail client. However, the patch only fixes the cross-site scripting issue on one of the listed browsers and fails to address a second vulnerability altogether, according to two security researchers who sent e-mail to the Bugtraq security e-mail list after the patch's release.

According to Microsoft's explanation of the issues, the first flaw can only be exploited when a user clicks on an HTML (Hypertext Markup Language) link on a Web page or in an e-mail message. That's not true, as code embedded in an HTML file can automatically execute, according to both Thor Larholm, a security researcher who has discovered a number of Microsoft vulnerabilities and maintains a list of unpatched IE holes online, and the Israeli security group GreyMagic Software, which has also discovered a number of browser vulnerabilities. As a result, users can unwittingly launch malicious code simply by opening an infected e-mail message.

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The patch doesn't completely fix the problem because the flaw resides in the dialogArguments component of IE, which is not addressed by the patch, both researchers said. Furthermore, though Microsoft claims the flaw only exists in IE 6, both researchers maintain that the problem is also found in IE 5.01 and 5.5.

"Microsoft is aware of the issues and is investigating the reports," a Microsoft spokesman said. Microsoft maintains that the patch does what the company said, but the company is also investigating the researcher's claims, the spokesman said.

After further testing of the patch, both Larholm and GreyMagic said that the patch also fails to adequately address a second vulnerability that it claims to fix, a problem that could allow an attacker to remotely read documents on a PC.

In the original vulnerability, Cascading Style Sheets (CSS), a component of HTML, could be used to remotely read files on an affected PC, according to GreyMagic's original advisory. Though the patch claims to address this issue as well, GreyMagic posted code on its Web site last Friday demonstrating that the vulnerability can still be exploited by using a URL that redirects the user, as opposed to accessing the files directly. Larholm sent an e-mail about the issue and his testing of it, as well as GreyMagic's update, to Bugtraq last Friday.

Microsoft maintained that the patch does what it is advertised as doing, and called the reports of the Cascading Style Sheets vulnerability "after-the-fact," in the words of a Microsoft spokesman.

The CSS vulnerability is a distinct issue from the one addressed by the patch and is being investigated by the company, he said.

The new bug reports "shouldn't raise any doubts about the efficacy of the patch," he said. "Microsoft still has confidence in the patch."

The patch at issue can be found via the link below.

This isn't the first time that a Microsoft patch has caused problems for users. Another IE patch, released February, caused the browser to crash.