You may have read that Cambridge Analytica harvested Facebook data from 87 million users accounts and used the data to build models to send targeted news stories to those users. Christopher Wylie, the former Director of Research at Cambridge Analytica and whistleblower on the use of the data said, "We exploited Facebook to harvest millions of people’s profiles. And built models to exploit what we knew about them and target their inner demons. That was the basis the entire company was built on.”
You can see what data Facebook has about you and which advertisers it sold your data to using this tool on Facebook's site and can read an article about the tool here. You can also learn if Cambridge Analytica harvested your data here.
Finally, for a thoughtful opinion article arguing that monetizing your data is an ineluctable part of Facebook's business model and therefore Facebook cannot be fixed but should instead be replaced is here.
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