Kenmore Over the Range Microwave. Brown stain trapped between front plastic window and inside of

Question

Brown stain trapped between front plastic window and inside of of microwave window. I know how to remove the door but was wary at disassembling it to get to the stain. If you push on the plastic window in front the stain moves along the door window. So it is a wet stain from moisture somehow entering the door. Didn't want to break any plastic tabs holding this all together. Wife wants new microwave because of this problem.