My Pontiac Grand Prix is leaking a brown substance up into the rear

[Curtis K]

floorboard.?
in reply to below: it looks like the liquid is coming up from two spots. one directly under the back of the driver seat and one at the very back just before the backseat starts.

 

[Ian F]

There are no fluids that could be leaking at the rear of the car. Sounds more like someone spilled something.