In a press release announcing that UK psychology professor Aleksandr Kogan and Cambridge Analytica have been suspended from Facebook, the Company explained how the user profiles were obtained:
The claim that this is a data breach is completely false. Aleksandr Kogan requested and gained access to information from users who chose to sign up to his app, and everyone involved gave their consent. People knowingly provided their information, no systems were infiltrated, and no passwords or sensitive pieces of information were stolen or hacked.
Although Kogan gained access to this information in a legitimate way and through the proper channels that governed all developers on Facebook at that time, he did not subsequently abide by our rules. By passing information on to a third party, including SCL/Cambridge Analytica and Christopher Wylie of Eunoia Technologies, he violated our platform policies. When we learned of this violation in 2015, we removed his app from Facebook and demanded certifications from Kogan and all parties he had given data to that the information had been destroyed. Cambridge Analytica, Kogan and Wylie all certified to us that they destroyed the data.
Beware of signing up for data-sharing apps. — Joe