Question Oc'd my CPU and it's above 70ºC just with browser opened

[kazurengan]

is this normal? i OC'd my CPU but i didn't expect the temperature to go this high
i'm using MSI afterburner with the fans on Auto, and for some reason the fans won't go higher than 40%

I'm using a i7-8700k
and asus tuf z390 i selected extreme tuning in BIOS

 

[rgd1101]

oc to what?
what the cooler?