Rear bumper very hot

Ive installed a Carlsson Sport exhaust on my fortwo.

I noticed that the central area of my rear bumper (just infront of where exhaust sits) is becoming extremely hot; to the point of not being able to touch it!

Not having driven my car with the stock exhaust, I am wondering if anyone of you face the same situation with your stock exhausts.

If yes, then I suppose its normal... If no, then can anyone advise if this can cause a fire?? Or what could the remedy be (apart from reinstalling the stock exhaust)?

Thanks!