AC condensate leaking into passenger side floor

If it is raining or when car is being washed, then you probably have a front window rubber leak. If all the time check if it only happens when heater is on. Probably a heater radiator leak.

this will be condensate from the fins of the ac evaporator in the car and is leaking onto the floor because the drain on the unit is blocked either in the hose or at the bottom of the ac box

You have a cracked condensation pan on your AC or a bad hose (could be cracked or clogged). You'll need to remove the dash to investigate which it is.

There is a drain coming out of the Heater & A.C. box it should go thru fire wall usally on passenger side.What kind of car?

This could be a sign the heater core or hose has gone bad and is leaking into the cabin since it is located inside the dash ifs its antifreeze it will have a sweet smell.
It could also be your AC condenser, or possible window seal.

is it only when the ac is on? there is a pan under the ac unit that has a hole in it to allow the condensation to empty. if that hole gets plugged it could cause the condensation to build up and back into the inside of that car. i unplugged mine and floor stayed dry

there may be some body rust around the window seal or in the air intake area, depending on your climate, condensation can sometimes drip of the AC system onto your feet

look under the car there are plugs located in the floor look to see if the plug has rotted , the ac condenser still condenses water even if it is not turned on check to see if the drain on the fire wall(located on the fire wall passenger side towards the bottom)is plugged with mud or debris, if it is not plugged the heater/ac unit shell may be cracked allowing water to seep, also check around the front window for leaks.

Is the leaking liquid antifreeze or clear water? Anti freeze is slimy. Ck your AC drain . its under the blower housinfg under the hood on the fire wall. The drain is easier to seeb from below looking yp. Squeeze it open and make sure it's clear. Good luck -Ned_

look at the firewall on the engine side and you will see a small stub hose coming out on passenger side about even with the bottom of the heater box inside. that hose drains condensation from the ac...clear it out and you will have a dry floor. (unless heater core is leaking but you didn't mention any overheat or coolant loss so likely that's not a problem)