There's no door and no light. It's just a very basic roughly sensor pixel-sized glitch in the data made a little worse by some compression it looks like. For a light to be that visible at that level of brightness to an orbiting spacecraft during daylight, it would have to be amazingly intense to start with. The compression darkness around the spot, if it were an actual physical object, would be nearly 550 feet wide. That would hardly be a secret.