S60 T5 Fuel Tank overflow?

I was filling my fuel tank recently, and following automatic shutoff of the pump, I noticed a gush of fuel run out from underneath the car directly below where the fuel filler opening is, as I pulled out the nozzle. Fuel continued to drip for several minutes. I have not noticed this before. I should add that the fuel pump nozzle had one of those rubber vapor retention collars on it. Is there an overfill shunt at the top of the fuel filler neck that prevents an overfill from running out the neck and down the body of the car? Or is there a leak in the fuel filler? Or none of the above?

Thanks!