Facebook said that most of its two billion users likely have had their personal information scraped and shared by third-party developers without their explicit permission.
The statement dramatically raises the stakes in a privacy controversy that has dogged the company for weeks, spurred investigations in the United States and Europe and sent the company's stock price tumbling.
The acknowledgement came in a Facebook blog post today in which the company for the first time detailed the scale of the improper data collection for Cambridge Analytica, a political data consultancy hired by US President Donald Trump and other Republican candidates in the last two federal election cycles.
The political consultancy gained access to Facebook information on up to 87 million users, most of them Americans, Facebook said. Cambridge Analytica obtained the data to build "psychographic" profiles that would help deliver target messages intended to shape voter behavior in a wide range of US elections.
But in research sparked by revelations from a Cambridge Analytica whistleblower last month, Facebook determined that the problem of third-party collection of user data was far larger still and, with the company's massive user base, likely affected a large cross-section of people in the developed world.
