Coinbase, Etoror, Ftx,Primexbt, Bitmex these are the ones I can think from the top of my head which I think have never been hacked at least thus far. Though, this may just be due to improved security or else no targeting attempted as hackers probz went for the lowest hanging fruit!
I'm not sure that because any exchange will have security holes and if it is a small sum they will not be public. Of course, if that exchange has lost more than $ 10 million, surely everyone in this market will know soon, so be careful before you deposit into the exchange.
I often use Huobi because this exchange is great for investing and is the largest exchange in the crypto market.