Crackers could ferret their way into a victim's email by exploiting the way that Exchange 2000 allows users to access their in-boxes over the Web.

Microsoft has issued a patch; the flaw revolves around the interaction between Outlook Web Access and Internet Explorer in handling message attachments.

If an attachment contains HTML code including script, the script will be executed when the attachment is opened, regardless of the attachment type. In the hands of even a modestly skilled attacker this could be used to create maliciously constructed emails designed to break into user's In-boxes, as Microsoft states.

In a security notice on the issue, Microsoft said: "If the user opened a [maliciously constructed] attachment in Outlook Web Access, the script would execute and could take action against the user's mailbox as if it were the user, including, under certain circumstances, manipulation of messages or folders."

This attack relies on the use of Outlook Web Access to read emails, emails opened locally aren't subject to the vulnerability, the flaw could be a relatively easy way to try a spot of industrial espionage - or worse - so it should be addressed sooner rather than later. ®

External links

Microsoft bulletin: Incorrect Attachment Handling in Exchange 2000 OWA Can Execute Script

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