Mine was doing it awhile ago. It wasnt coming in through the cabin filter. Instead it was coming between the HVAC assembly and the car's body. Degreased around the housing with some alcohol, then sealed it up with some silicone. Havent had a drop inside the car since then.
The problem will be compounded if the weatherstriping between the cowl panel and the windshield is bad. It will let the water drop right onto the HVAC unit.
The drains for the cowl are along the outer edge, IIRC. Ill check the parts car when I go outside.
Ill have to check out the filter from AZ. If I need to replace mine when the car is apart, I will now know where to save a few bucks.
EDIT: Last few days is an understatement. Its been over a week now.
Its making my repair work go very slowly.