How many Facebook users were affected by the Cambridge Analytica data breach? Up to 87 million users were affected.
The figure came from Facebook’s 2018 estimate after the company investigated data obtained through Aleksandr Kogan’s personality-quiz app, “This Is Your Digital Life.” About 270,000 people installed the app, but an older Facebook platform feature allowed apps to collect information about many users’ friends as well. That made the exposed population vastly larger than the number who downloaded the app.
The data was passed to Cambridge Analytica, which used it for political profiling and targeted advertising. The 87 million figure was an estimate, not a count proving that every affected profile was used in the same way. Earlier reports often cited 50 million users, based on initial disclosures; Facebook later revised the public estimate upward.
The scandal helped trigger congressional scrutiny, regulatory investigations and major changes to Facebook’s third-party app permissions. The related Facebook–Cambridge Analytica data scandal article provides the most focused overview.