Isn't hacking illegal?
Not necessarily.
'Hacking' without permission is illegal.
But Cyber security researcher, penetration tester, bug bounty hunter, ... all are white hats.
They do 'hacking' for a living - in a completely legal way.
Who do you think is auditing companies and banks ?
You need 1) 'real' auditors (who audit the processes inside of the company) and
2) penetration tester to successfully find security flaws which can be exploited.
P.s. I do not know what kind of website this is, neither did i ever visit it.