Purchased my car new in 9/08, car was perfect up to now but after 12 mo. it started smelling MOLDY, after checking around I found water had accumilated under the carpet in the passenger side, took it to the shop and they said that the AC condenser was leaking inside the passenger side of car, flooding the front passenger side and rear area under the carpets.
According to what I have read on other forums, that's a common problem with the 2008 Malibu.
The shop changed out all the carpets and padding plus they say they cleaned in interior with a solution to get rid of the mildew and moldly smell, but the MOLDY smell was still there.
Next they sprayed the ac inside the car with some kind of spray that was to get rid of the smell per GM, after doing that twice, it still smell Moldy, but not as much.
Have to return next week and see what's next!

 

Thats got to be very frustrating with a fairly new car still under warranty. I wander if the smell has now seeped into the fabric and whatnot of the seats. Ask them to replace them, I would def not want to put up with that smell.

 

this just happened to my car...it's not the AC leaking, it's actually the evaporator drain...here's the service bulletin:

#09-01-37-002B: Front and Rear Passenger Floor Carpet Wet (Inspect White Plug in HVAC Evaporator Drain and Apply Sealer to Front of Dash Area) - (Mar 26, 2010)

the water actually goes out of the vehicle through the drain pipe, and then comes back in from the outside of the pipe...the turbulence of the air underhood actually pushes the water back along the outside of the tube, through the seal and back into the passenger side...my entire passenger side floor was soaked and i'm still trying to dry it out 5 days later...there's a seam sealer you need to buy and surround the outside of the drain pipe with it...seems to have worked for me...but i've got to drive it a bit more to make sure it worked...

 

I Found my carpet wet on rainy days. After 2 days i found it was comimg down t he windheld on the outside to the bottom under the sheld and into the air intake for your heat and a-c then onto floor. After I took wipper arms off (2 10mm nuts) I took off plastic sheld and thar was a rubber molding that fell off . I put it back on with glue. Also I replaced the cabin air filter. I put it back together and it works fine.(no moor wet carpet).