Microwave oven leakage preventable?

My Panasonic microwave oven has been leaking and arcing at the door but seems to be heating okay. There is an obvious discoloration on the door and the oven. The location is top right hand corner just outside the oven opening. The size is  1 inch x 0.33 inch on the door (a small bulge)  and the oven ( a small depression). I don't think it is leaking outside the oven since there is supposedly an adjacent microwave leakage block on the door.

Question:

Has anyone experience with such leakage?

Is it likely to get worse?

Is there any way to repair the damage and eliminate the arcing?

What is the danger if I keep using it?

Thanks a lot for your help.