content: You're seeing the rubber gasket pop out.  The glass has a 2-3mm polyester film on the back that attaches with a strong adhesive.  The edges of the film are mechanically attached to the window frame.  I did see a gap open up when the frame flexed that they could have jammed something into, but breaking the glass away and puncturing the film at an edge or corner, and heat, is the weak point of that stuff.