IE-6 privacy solution backfires

Several malicious possibilities

It may seem ironic, but privacy functionality in IE6 makes it possible to launch several attacks against the browser, and against Outlook and Outlook Express, security researcher Thor Larholm has discovered.

"The privacy features added in IE6 to help protect a user's privacy by giving them direct control over cookie management allows any site to read any other site's cookies, in effect removing all privacy. Further, this hole extends to other protocols, allowing you to execute arbitrary commands on the user's machine as well as take over MSN Messenger," Larholm told us.

At issue is IE's dialogArguments interaction, which is supposed to prevent objects being passed to a dialog, but doesn't quite.

IE regulates interaction between remote pages by comparing the location of the originating page and the dialog page, Larholm says. If they match, interaction is allowed. But he's discovered that it's possible to use HTTP redirects to get around the restriction and provides several harmless examples in his advisory, which readers may play with.

We tried them against IE6 on a fully patched XP-Pro box, and they worked as advertised. While the examples are harmless, the potential for mischief is considerable. There is no patch, but a perfectly good workaround is simply to disable scripting.

He tells us MS was notified on 18 March, and is currently evaluating the need to issue a patch. Larholm also maintains a page of unpatched IE holes, with which he hopes to inspire some action back in Redmond. ®

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