All 10 of Facebook’s most popular apps, including Farmville and Texas HoldEm Poker, are among those leaking the unique ‘Facebook ID’ number to outside firms. The Wall Street Journal said at least 25 firms were being sent the Facebook IDs, which they were using to build profiles of web users, and in some cases, even track their web browsing. Facebook stopped users accessing several apps thought to have been leaking personal data. It’s not known if the developers knew their apps were leaking data.
Source: https://thehackernews.com/2010/10/facebook-apps-leaking-personal-data-to.html