I had a crack in the glass on mine old microwave years ago. I was concerned so bought a cheap microwave leak detector. It showed that there was leakage around the door seal but it was only noticeable when the detector was on or very close to the door. A few inches from the door showed nothing.

My conclusion was that as long as I didn’t put my face on the glass I’d be OK. A couple paranoid precautions I take is to step back once I start a microwave and I try to wait until the timer stops the microwave before I open the door.

I have since had two kids so I guess the leak wasn’t too bad