This is very common.
I had to replace both front wings a few years back due to sponges in the wings.
Daft thing, I have just got a 2017 plate Alfa Giullietta and they have placed sponges in the front wings too. So I need to have a word with the dealer when I have to visit.
If anyone has not checked for this daft idea, I would recommend doing so before winter sets in and salty water collects in the sponge.