water leak in passenger floor

Most sunroofs have a drain tube from each corner that snakes down through the A pillar and rings to the outside of the car.

Crap gets built up and blocks one or more of the drains, causing the water to have to flow somewhere else, and then somewhere else is your headliner. Boston, the drain tube gets plugged near the sunroof itself so you may want to try compressed air to clear it but from the other end so you don't just blow the crap further down into the tube where it never comes out. It's up to you. Other people take a medium gauge piece of electrical wire with insulation on it and the conductor and cut flush try to ream out the drain. You have to be very careful not to tear the drain tube if you take this approach. The tube usually exits near or into the wheel well closest to that corner of the vehicle