Corsair C70 Computer Case Front Panel USB Shocks Me?

My Corsair C70 case has 2 USB 3.0 connectors in the front and whenever I plug anything into them the other end of the cord shocks me. For example, a printer's USB connector and my iPhone 4s charger have shocked me when fully inserted into the USB slot. Can anyone explain why this is happening and how to fix it.

Most likely cause -- the cord you're using is defective and exposes the leads to your touch

less likely -- the front panel port is miswired -- has polarity wrong -- this would be inside the case. Diagnose with a voltmeter… The exterior metal end should be neutral to ground [the computer case is grounded].

even less likely -- frayed wiring inside case or power supply is allowing 12 volts to 'leak' into the USB circuit [which is 5 volts]. Voltmeter finds this, too.

even more remote -- somehow the 110/220 volt [AC] power supply input voltage is "leaking" to the USB port. I've never heard of this happening, but I suppose it is possible -- since the USB port's leads go to the mobo [motherboard], I'd think the mobo would be fried and the computer wouldn't work at all -- and, someone [remote chance] might have intentionally miswired the thing inside the case.