Yeah, but that's not how the exploit would work. If you read the article, the "backdoor" is that WhatsApp could "generate" a new private key without your knowledge. Except that instead of generating a key, they'd use a well-known key. From there, they could give that key to state actors, or they could decrypt the traffic themselves and give it to state actors.
Either way, you need server side control of WhatsApp.
