Mr Musk, through his tweet, apparently implied that WhatsApp users should switch to Signal. His tweet was liked and retweeted thousands of times.
Signal is a well-known privacy-focused messaging app, that is widely used by security experts, privacy researchers, academics, and journalists around the world. The Signal protocol also underpins WhatsApp's end-to-end encryption, although one key difference is that Signal is open source, while WhatsApp is not.
Verification codes were delayed because of the sudden influx of users on the Signal app. "We are working with carriers to resolve this as quickly as possible. Hang in there," the app tweeted on Thursday. The issue has been resolved now.
Use Signal— Elon Musk (@elonmusk) January 7, 2021
Mr Musk has often sparred with Mark Zuckerberg over several topics and taken shots at him, the most recent being a meme on Twitter.
The meme was connecting the beginning of Facebook, which the billionaire described as a "website to rate women on campus", to the siege of Capitol Hill in US described by a domino effect.
This is called the domino effect pic.twitter.com/qpbEW54RvM— Elon Musk (@elonmusk) January 7, 2021
They have also famously disagreed on Artificial Intelligence with Mr Musk saying the Facebook CEO's "understanding of the subject is limited." He also tweeted "Facebook sucks" during a clash with the company's artificial intelligence lead.
WhatsApp's policy change move has caused quite a stir, with reports claiming that it makes sharing data with Facebook mandatory. However, WhatsApp has issued an official statement clarifying that its data-sharing practices with Facebook have not changed. The changes that will go into effect next month look to address data sharing between WhatsApp and Facebook business accounts.