It's not as clear cut.
Same thing happened to me two years ago. Toys in storage that got moldy in storage. Mold on packaging is very hard to kill. I had to use alcohol (hey, everything goes better with alcohol!), and dab it gently on the boxes. Don't rub!
As for costumes on figures: some fabrics had handle dish soap and a tiny dash of bleach. The bleach is the only thing that will kill the germs 100% sure.
Be careful with figures like Big Jim. The mold penetrates the rubber and plastic. Sometimes, like my Big Jim collection, I had to say "it's dead, Jim". They looked like Moss Man.
Mold is a terrible thing to happen to your stuff. In the end, my insurance covered some of it. Some items that I treated, had the mold return months later. Keep your stuff as dry as possible now. Get it in a warm and bone dry environment and keep it there so the mold dries out and dies off.
Most of my book collection in storage was a write off.
On a related topic: anybody know if "foxing" (the brown spots) on book pages is something that keeps spreading? Or is "contagious" (infecting other books)?
"Everything has an end.
Except sausages, which have two..."