No stranger to public discontent, Facebook Inc. is digging out of one of its biggest crises yet. The personal data of up to 87 million users, mostly in the U.S., was obtained by an analytics firm that, among its other work, helped elect President Donald Trump. In response to that revelation, lawmakers and regulators in the U.S. and U.K. increased their scrutiny of the social media giant, and at least some Facebook users canceled their accounts. The uproar has only added to the pressure on Facebook and Chief Executive Mark Zuckerberg over how the company was used during the 2016 presidential campaign to spread Russian propaganda and phony headlines.

1. Who took what from Facebook?

During the summer of 2014, the U.K. affiliate of U.S. political consulting firm Cambridge Analytica hired a Soviet-born American researcher, Aleksandr Kogan, to gather basic profile information of Facebook users along with what they chose to “Like.” About 300,000 Facebook users, most or all of whom were paid a small amount, downloaded Kogan’s app, called This Is Your Digital Life, which presented them with a series of surveys. Kogan collected data not just on those users but on their Facebook friends, if their privacy settings allowed it — a universe of people initially estimated to be 50 million strong, then upped to 87 million. The app, in its terms of service, disclosed that it would collect data on users and their friends.

2. Did Kogan have Facebook’s permission?

In a general sense, yes. Since 2007, Facebook has allowed outside developers to build and offer their own applications within its space. When Kogan offered his app, Facebook also allowed developers to collect information on friends of those who chose to use their apps if their privacy settings allowed it. “We clearly stated that the users were granting us the right to use the data in broad scope, including selling and licensing the data,” Kogan wrote in a March 18 email obtained by Bloomberg.

3. Then what’s the issue here?

Facebook says Kogan “lied to us” by saying he was gathering the data for research purposes and violated the company’s policies by passing the data to Cambridge Analytica. Kogan says his app’s terms and conditions specifically allowed “commercial use.” Facebook says that after it learned of the situation in 2015, it removed Kogan’s app and demanded that he “and all parties he had given data to” destroy the data.

4. Has the data been destroyed?

The New York Times — which broke the story along with The Observer of London — reported on March 18 that emails and documents suggest the firm “still possesses most or all of the trove.” Cambridge Analytica has maintained that it deleted all the data Kogan provided and, at Facebook’s request, “carried out an internal audit to make sure that all the data, all derivatives, and all backups had been deleted.” Facebook’s chief technology officer, Michael Schroepfer, said in an interview on April 5 that pending the results of investigations, “we don’t know exactly what they have.”