Easily the headline for this week. In bullet points:
- Cambridge Analytica had an app called "thisisyourdigitallife" . It was installed by about 300.000 people who gave it access to their data.
- At the time any Facebook app could also access data from friends of their users. As such they gathered info on 50 million people, mostly US citizens.
- Later, after that data-from-friends policy was changed, Facebook got wind of the data harvesting that occurred. They 'made' the people responsible delete the data, but apparently they didn't comply.
- Facebook never disclosed that it knew of the breach/leak, and apparently even lied about it in hearings related to the Russia election meddling investigation.
The above article by the Guardian gives a very good overview.
Mark Zuckerburg wrote a post outlining the story from his point of view here. He also says they will look for similar instances of data harvesting and implement stricter app controls.