WhatsApp has been exploited before with a zero-day, check the Complaints section in this link:
https://en.m.wikipedia.org/wiki/Pegasus_(spyware)
The reality is WhatsApp and Signal will continue to be high-value targets for exploits given the number of users, cloud infrastructure reliance and promise of secure communications, so it's a wise idea to avoid them for defence matters.
The one thing that could cause serious porting pain would be the need to support high/variable frame rates. That could require a whole bunch of code to be refactored.