Or might be just dirt or some cleaning spray residue I got a Nucleon Convoy for real cheap, from a japanese seller, translation wasnt great for what he was selling, but he did for a steal price for these details The figure had some kind of dirt on the back ramp, easily cleaned with alcohol. However, the box, has these strange spots I dont think is mold, but i wouldnt want to take any chances, what do you think? Inside the box, is clean, only the top is affected and the right flap slightly
Lighter fluid and lots of it. Oh and paper towel. If it is mold, the lighter fluid should get rid of it and depending on how bad it is you may need to do several passes letting the lighter fluid dry in between each pass.