The Risk of Hacking Cryptocurrencies

If all developed country central banks created digital currencies, wouldn't they all be vulnerable to an attack? And then what happens to the entire financial system in that sense? I mean, that's a very scary prospect. But if you use this well established er, you know, a high valuable cyptocense, then the risk is extremely limited. You get your money stolen when you have your money outside the bank,. This is not the fault of the banks. This is you having your money not in a safe environment.