By now you've no doubt heard about the Cambridge Analytica data scandal, aka why everyone is pissed at Facebook right now. In short, potentially 87 million people had their data stolen via a quiz app, and this data was then sold to the embattled British political firm, which then used the stolen data in an attempt to influence the last election. The blame has largely fallen on Facebook's previously cavalier attitude toward providing user data to third-party app developers.
Starting on Monday, April 9, users will receive a notification at the top of their Facebook feed called "Protecting Your Information" with a detailed message and a button that will allow you to change your privacy settings.
The type of notification you get will tell you whether your data might have been compromised. If you get the one on the left (shown below), chances are your data was safe. If you see the one on the right (also shown below), with "SEE HOW YOU'RE AFFECTED" at the bottom, there's a chance your data was stolen.