First thought is the AC evaporator drain. Look for a drain tube under the car, near the center of the firewall. Probably plugged up with crud.

Maybe you can see the drain hose inside? Look for the bottom of the air duct, look for a funnel-shaped part facing forward to a drain hose. Some years/models it's visible, others it goes directly thru the firewall & you can't see it down at your feet.

If you go under the car, sometimes you can squeeze the drain hose & get it to flow, sometimes you have to poke it. Use plastic weedwacker string, it won't poke thru like a sharp coathanger. Either way, be careful about getting a faceful of black wet smelly crud.

If the stuff leaking under the dash isn't water, then post back what it is.
Anti-freeze? - bad heater core.