This includes ads targeting purposes on Facebook pages. The information shared will include phone number which the user used to verify their account and the last time the user used the service. The information shared is not something you share with a data mining tech giant. Though, users can partially opt-out from sharing the information to WhatsApp.
How to restrict WhatsApp from sharing your user data
Unfortunately, there is no way to totally opt out apart from deleting your account from not using WhatsApp. When the notification pop out, don’t tap Agree, instead tap read which is highlighted in blue. You will then see a control at the bottom of the screen. Please uncheck the box.
Remember: You may not totally reject sharing your user data with WhatsApp .