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IDG News Service - A feature in Apple's Safari browser designed to make it easier to fill out forms could be abused by hackers to harvest personal information, according to a security researcher.

Safari's AutoFill feature is enabled by default and will fill in information such as first and last name, work place, city, state, and e-mail address when it recognizes a form, wrote Jeremiah Grossman, CTO for WhiteHat Security, on his blog.

The information comes from Safari's local operating system address book.

The feature dumps the data into the form even if a person has entered no data on a particular Web site, which opens up an opportunity for a hacker.

"All a malicious website would have to do to surreptitiously extract Address Book card data from Safari is dynamically create form text fields with the aforementioned names, probably invisibly, and then simulate A-Z keystroke events using JavaScript," Grossman wrote. "When data is populated, that is AutoFill'ed, it can be accessed and sent to the attacker.'

Proof-of-concept code for an attack has been published on the blog of Robert Hansen, CEO of SecTheory. Grossman also posted a video of the attack on his blog.

For some reason, data beginning with numbers won't populate text fields and can't be obtained. "Still, such attacks could be easily and cheaply distributed on a mass scale using an advertising network where likely no one would ever notice because it's not exploit code designed to deliver rootkit payload," Grossman wrote.

"In fact, there is no guarantee this has not already taken place," he wrote. "What is safe to say is that this vulnerability is so brain dead simple that I assumed someone else must have publicly reported it already, but exhaustive searches and asking several colleagues turned up nothing."

Grossman reported the problem to Apple on June 17, but he has yet to receive a personalized reply.

To avoid this issue, users can simply disable AutoFill Web forms, he wrote.

Send news tips and comments to jeremy_kirk@idg.com