Data breach. Cambridge Analytica scandal: the biggest revelations so far. Below is a statement copied from the wikipedia about a data breach on facebook.
“The Facebook–Cambridge Analytica data scandal was a major political scandal in early 2018 when it was revealed that Cambridge Analytica had harvested the personal data of millions of peoples’ Facebook profiles without their consent and used it for political advertising purposes. It has been described as a watershed moment in the public understanding of personal data and precipitated a massive fall in Facebook’s stock price and calls for tighter regulation of tech companies’ use of personal data.”
Cyber Ethics 