suggest revise carefully the rubber seal at the square corners at the upper part of the door. make sure they are tighting firmly the metal, thus avoiding capilarity that will drive the water inside the car to the floor trough the pillar that holds the front safety belt
Antifreeze leaking from the heater core.
Passenger side? Could be heater core leaking? Bad seal at windshield? Door seal?
Passenger side floor? Could be leaking heater core
you could have a heater core leaking or your windshield is leaking and the water is running down behind the dash and onto the floor.
Heater core is leaking
There is a drain on the outside firewall that is clogged.
heater core may be leaking or hole in floor
Leaking heater core.
Heater core leaking?
Are you running the air conditioner? If the drain line is plugged, it will leak water (condensation) onto the passenger side floor.
If your talking about coolant leaking on the passenger floor then it means your heater core is leaking and needs to be replaced.
most likely cause is your heater core leaking