It is a question that not all of will think about on a daily basis, so a simple home experiment can help you to find out if your microwave has some sort of a radiation leak.
A good question to kick it off is, do cell phones that are placed in a microwave still receive a signal? What is the difference between microwave oven radiation and the signals used by your phone?
In the video, Physics Girl says that if you place your phone in a microwave and close the door, it will only be able to receive an incoming call if there's a leak. She places a phone in a microwave and asks some of her friends to call it, thus demonstrating that the oven's protective casing is not impervious to radiation and that signals can still pass through.
The microwave is shielded by a Faraday cage that is designed to block any microwave radiation. The surprising results show that the casing is not a perfect Faraday cage, which use mesh to block electromagnetic wavelengths from passing through.
Watch the video by Physics Girl for more info: