Risk: Informational
As some of Facebook's code is published online, concerns are raised about the security of social networking websites.
Facebook has undergone a range of criticism recently - there have been claims that the site's founder stole the idea for the site from two ex-colleagues, advertisers have withdrawn their support following their adverts being displayed on controversial pages and people have been warned against posting too much personal information on such websites.
Facebook blamed the leaked code on a bug and said that it was published accidentally, adding that users should not be concerned. Facebook's spokeswoman, Brandee Barker, said: "It was not a security breach and did not compromise user data in any way."
Those who use Facebook are warned to do so with caution and are urged not to post personal information such as their mother's maiden name or place of birth.