A hack of millions of Facebook users’ data has revealed that the company’s CEO Mark Zuckerberg uses the secure messaging app Signal, one of the main competitors of the Facebook-owned WhatsApp.

Dave Walker, a cybersecurity researcher, discovered that Zuckerberg was among more than 533 million Facebook users whose information was leaked in the 2019 hack, Mashable reported.

“In another turn of events, Mark Zuckerberg also respects his own privacy, by using a chat app that has end-to-end encryption and isn’t owned by @facebook,” Walker tweeted, along with a photo of Zuckerberg’s redacted phone number, which he linked to a Signal account.

Signal, one of WhatsApp’s main competitors, is an encrypted messaging app, meaning that the company cannot access any messages or calls made by users on the app.

After the news broke of Zuckerberg’s supposed use of Signal, the company retweeted a link to the story writing: “With the May 15th WhatsApp Terms of Service acceptance deadline fast approaching, Mark leads by example.”

WhatsApp’s plans to update its privacy policy earlier this year were put on hold amid public outcry over privacy concerns. In a recent blog post, the company said the update will not affect personal messages and that the changes are related to “optional business features.”

Facebook CEO Mark Zuckerberg and the Signal messaging app.

Details from more than 533 million Facebook users have been found available on a website for hackers. The information appears to be several years old, but it is another example of the vast amount of information collected by Facebook and other social media sites, and the limits to how secure that information is.

The availability of the data set was first reported by Business Insider. According to that publication, it has information from 106 countries including phone numbers, Facebook IDs, full names, locations, birthdates, and email addresses.

"This is old data that was previously reported on in 2019," the Menlo Park, California-based company said in a statement. "We found and fixed this issue in August 2019."
Fox Business has reached out to Facebook with a request for comment but did not hear back before publication.