Suits: Nissan Navara D23 NP300 Dual Cab models
This is the stop light located on the body of the vehicle above the rear window.
Common to be cracked and leak water into the cabin.
A good sign it is cracked is water appearing on the inside of the rear window.
Note: as this is a newer model, the bracket that comes with it may be slightly different, but it is designed to suit all Dual Cab models from 2015.