Twitter Worm Fixed

Strategic Security Survey: Global Threat, Local Pain

Twitter says that it has fixed a cross-site scripting (XSS) vulnerability that allowed several XSS worms to spread across the site early Tuesday morning.

"We’ve identified and are patching a XSS attack; as always, please message @safety if you have info regarding such an exploit," the company said in a status message posted at 6:25 am PT.

Twenty-five minutes later, Twitter updated the message to say that the fix was complete.

The vulnerability involved improper input cleansing: Twitter failed to deactivate JavaScript code elements in user input. This allowed users to craft malicious tweets that executed when another user allowed his or her mouse arrow to pass over the tweet, sending more infected tweets to the victim's followers.

The discoverer of the vulnerablity was a Japanese developer by the name of Masato Kinugawa, according to The Guardian. Kinugawa's work was then expanded upon by other developers around the world, several of whom created worms that redirect users to adult Web sites.

Graham Cluley, senior technology consultant for Sophos, a U.K.-based security company, notes that one of the victims was Sarah Brown, wife of the former British Prime Minister. After being hit by the worm, Brown's account included a tweet redirecting visitors to a porn site in Japan.

F-Secure, a security company based in Finland, says that while Twitter may have fixed the problem, it expects problems to continue. "It's perfectly possible that there will be more malicious attacks, possibly combining this technique with browser exploits," the company said in a blog post.

A week ago, Twitter introduced "re-engineered" version of its site, promising a better user experience.