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

The patch, which was released late 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 fixes only the cross-site scripting issue on one of the listed browsers, according to two security researchers who sent e-mail to the Bugtraq security e-mail list after the patch's release.

Flawed Fix?

According to Microsoft's explanation of the issue, the flaw can be exploited only when a user clicks on an HTML 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. Larholm's assertion is backed by 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.

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 Investigates

Microsoft representatives say the current patch performs as necessary, but that the company is looking into the latest allegations.

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

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

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