Signal may not be as popular as Facebook’s WhatsApp, but even Facebook CEO Mark Zuckerberg may use the competing product.

Facebook caused a furor when it announced it would share WhatsApp user data with other Facebook-owned companies. The fallout was severe, with many users switching to the more secure Signal. Elon Musk also came out as a vocal proponent of Signal in the aftermath, further driving its growth.

Interestingly, it appears Mark Zuckerberg also uses Signal. Days ago, data for 533 million Facebook users was leaked online. Although the data is from at least a couple of years ago, it still includes a wealth of information. Security researcher Dave Walker perused the data and found Zuckerberg’s information was part of it.

Even more telling, the phone number listed for Zuckerberg is also associated with a Signal account.

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

This is the number associated with his account from the recent facebook leak. https://t.co/AXbXrF4ZxE

— Dave W. (@Daviey) April 4, 2021

Obviously, simply having an account doesn’t mean Zuckerberg regularly uses Signal. Nonetheless, it’s an interesting discovery.