Facebook apps leak information - Symantec

Symantec has found that certain Facebook applications have been inadvertently handing advertisers access tokens to access Facebook accounts over the Web, PC World Business Center reported.

Those tokens include strings of numbers and letters that can be used by a browser to access Facebook accounts over the Web.

"Access tokens are like the 'spare keys' granted by you to the Facebook applications," Symantec said in a blog post. "Each token or 'spare key' is associated with a select set of permissions, like reading your wall, accessing your friend's profile, posting to your wall, etc."

"We estimate that over the years, hundreds of thousands of applications may have inadvertently leaked millions of tokens to third parties," Symantec said. Facebook were not immediately avai;abled for comment.

The tokens were reportedly leaked in referring URLs that Facebook applications passed on to advertisers and others.

Symantec said it's not clear whether anyone realized that the problem existed, so it's possible that nobody has taken advantage of the bug to snoop on users.

Facebook has now fixed the problem, but it could still be a big problem for users, according to Symantec. That's because these tokens may still be in circulation, stored in server log files or in other places on the Web.

One of those access tokens will keep working until the Facebook user changes his password, so Symantec said that concerned users should change their Facebook passwords, like "changing the lock" on their Facebook account.

The issue doesn't affect Facebook applications that use the newer OAUTH2.0 authentication system, Symantec said.