Yes, WhatsApp has been hacked many times but there are limitations in the ways to hack WhatsApp remotely
Here you find some ways through which WhatsApp can be hacked remotely:
Hackers can hack into others' WhatsApp accounts by sending insecure links that makes you enter into, making them easily
A security flaw was detected as spyware was detected through a WhatsApp voice call. You can find it to download programs.
WhatsApp can be hacked by increasing apps such as mSpy, and that is through the stealth mode feature. After that, it spies on the data and gets access to his private messages.