Facebook (NASDAQ: FB) apologized for a “breach of trust” in full page ads in U.S. and British newspapers Sunday. The breach involves misused data from millions of Facebook users. The ads appeared in The New York Times, Washington Post, and Wall Street Journal, as well as several other well-known publications.

The ads featured black text on a white background with the Facebook logo. The ad read in part: “We have a responsibility to protect your information. If we can’t, we don’t deserve it.” Facebook Chief Executive Mark Zuckerberg signed the ad.

Reports have emerged that 50 million Facebook profiles were mined through an app created by a Cambridge University professor and then sold to Cambridge Analytica. The psychology professor, Aleksandr Kogan, said he was using it for academic purposes. The transfer of the data to a third party was in violation of Facebook’s terms of service. The company said it deleted the data in 2015 when Facebook alerted them that it had been improperly shared.

Cambridge Analytica worked for Donald Trump’s presidential campaign. The firm was created by conservative billionaire Robert Mercer and was previously led by conservative activist Steve Bannon.

Top officials from the firm have claimed credit for President Trump’s surprising 2016 victory. Its CEO, Alexander Nix, said in undercover footage that the company was responsible for much of the Trump campaign’s activity. Nix has since been suspended from his position at the analytics company. Facebook announced last week it was suspending Cambridge Analytica’s account.

In a blog post on March 21, Zuckerberg announced a slew of changes aimed at preventing another Cambridge Analytica situation. Now, developers will only receive a user’s name, profile photo, and email address when someone signs in through Facebook. More detailed information will be made available only after getting permission from Facebook. If the app hasn’t been used for three months, Facebook will cut off the app’s access to an account holder’s data.

A new poll shows a significant erosion of trust in Facebook, with only 41 percent of Americans saying that they trust Facebook to obey laws that protect their personal information. A #DeleteFacebook campaign has taken root, with Tesla CEO Elon Musk as one of the most prominent supporters after deleting the Tesla and SpaceX Facebook pages.