Facebook apologized for a data breach. CEO Mark Zuckerberg took out full-page ads in newspapers. He was being criticized for his slow response to news of the breach. A group of consultants called Cambridge Analytica is accused of using data on up to 50 million users to benefit Donald Trump's presidential campaign. Zuckerberg said: "This was a breach of trust, and I am sorry....We're now taking steps to make sure this doesn't happen again."
Mr Zuckerberg said Facebook should have done more to protect data. Facebook was warned about its weak data protection in 2011. Mr Zuckerberg outlined what Facebook would now do. He said: "We're investigating every single app that had access to large amounts of data...We expect there are others. The value of Facebook fell by $75 billion this week. Many users have abandoned their Facebook pages, in calls to #deletefacebook.