Voltage regulator damaged?

I had been running a Seeeduino Mega on a +12V source for some time with no issues. Then I managed to ground the 5V pin. The MCU got really hot, even melted a rubber band that was near. Now whenever I plug the board to a 12V supply it immediatelly heats up to >75C! Purrs like a kitten when running from USB though.

The theory is that the 5V regulator got damaged when the short occured, and now it's putting out a higher voltage. I'll measure the output when I get home, but for now, is this a known failure mode? Are there any periferal (around the reg) discretes that often fail during an overload like this or is it a regulator failure?

if it works on usb, but not external power, it is the regulator blown.

if you still need it to work on external power you could just build a small regulator circuit on a protoboard and connect the output to the 5v pin.

Thanks, I'll do that.