https://www.theverge.com/2018/4/9/17214814/facebook-data-notification-cambridge-analytica

Facebook has started notifying millions of users that were affected by the Cambridge Analytica privacy scandal. As many as 87 million Facebook users had their information improperly obtained and used, and it has taken Facebook nearly three years to notify its users of the privacy problems that were first uncovered in 2015.

Facebook is now displaying a link at the top of the News Feed today, pointing users to remove apps they no longer need. A Facebook spokesperson confirmed to The Verge that “the notification is rolling out over the course of today.” If your data was improperly obtained, Facebook will share a “how you’re affected” link and explain that a website a Facebook friend may have used was able to steal Facebook information and share it with Cambridge Analytica.