According to WGME, 70 million of the affected users live in the U. S.

If your account was one of those affected, at some point today (April 9th), you'll receive a detailed message in your newsfeed.

Additionally, all 2.2 BILLION of the social media service's users will get a message called "Protecting Your Information".  It contains a link to see what apps they use and what information they have shared with those apps. If they want, they can shut off apps individually or turn off third-party access to their apps completely.

Cambridge Analytica whistleblower Christopher Wylie originally said that more than 50 million people were compromised by a personality quiz that collected data from users and their friends.  However, in a recent NBC interview, he now says more than 87 million users could have been affected.

Facebook's Mark Zuckerberg said Facebook came up with the 87 million figure by calculating the maximum number of friends that users could have had while the suspect app was collecting data, but because they don't have logs going back that far, there really is no way to determine the exact number.