If your oven glass is broken or cracked we wouldn’t recommend you using the oven.
The inner oven glass is a thermal barrier. Without the inner panel, all the heat is going on the outer glass panel. As a result, this will become incredibly hot. Plus there is a danger of seeing the outer panel shatter as it’s not designed to receive very high temperatures. The inner panel is to retain heat and the outer panel is for viewing.
This is why you should replace the panel or get a new oven. It would be more cost effective to just replace the glass.
Even if the glass hasn’t completely shattered and it’s just got a crack, we would still advise not using the oven. The reason being is there is a safety issue and that the outer piece won’t isolate the heat. This will increase your energy bill as it will take longer to cook food.
There are many reasons why your oven glass can all of a sudden explode into tiny little pieces. Accidentally bashing or hitting the glass causes the glass to shatter or crack. Over time the high temperatures in the oven can develop the crack and this causes the glass to break.