Some Facebook applications have been leaking user information — specifically, Facebook user IDs — to third party companies, The Wall Street Journal reports.

The apps in question have a huge combined userbase; according to the WSJ, all of the 10 most popular Facebook apps are guilty of giving away user IDs to third parties, specifically Internet research and advertising companies.

These include Zynga’s FarmVille, Texas HoldEm Poker and FrontierVille, according to AppData, Farm­Ville alone had more than 80 million users in February 2010.


Facebook confirmed some of the issues in a blog post, claiming most of the apps in question shared the user IDs inadvertently, due to “technical details.”

“Our policy is very clear about protecting user data, ensuring that no one can access private user information without explicit user consent. ... It has come to our attention that several applications built on Facebook Platform were passing the User ID, an identifier that we use within our APIs, in a manner that violated this policy,” the post said.

Earlier this weekend, Facebook blocked LOLapps, one of the biggest social games providers on the Facebook platform, due to “violations of Facebook’s terms.” The WSJ claims that some of the apps created by LOLapps were also transmitting user info to third parties. LOLapps (whose apps have now been reinstated on Facebook) has confirmed this was the case in a blog post, claiming it shared the info inadvertently.

Facebook also said that “knowledge of a UID does not enable anyone to access private user information without explicit user consent.”

Although Facebook claims it’s doing everything it can to preserve its users’ privacy, this latest incident won’t do much to convince its users that this is really the case.