Researchers find serious spoofing flaw in Firefox

Aviv Raff, an Israeli researcher best known for ferreting out browser flaws, revealed the Firefox spoofing vulnerability on his personal blog, and posted a demonstration video there. He did not go public with any proof-of-concept code or working exploit, however.

According to Raff, Firefox 2.0.0.11 -- Mozilla Corp.'s most current version -- fails to sanitize single quotation marks and spaces in what's called the "Realm" value of an authentication header. "This makes it possible for an attacker to create a specially crafted Realm value which will look as if the authentication dialog came from a trusted site," said Raff.

Raff outlined a pair of possible attack vectors. One would rely on a malicious site that included a link to a trusted site -- a well-known bank, say, or a Web e-mail service such as Gmail or Hotmail -- that when clicked would display its usual log-on dialog. In the background, however, the attacker would have crafted a script that exploited the Firefox vulnerability to redirect the username and password entered by the user to the hacker's server instead of the real deal.