I was given a pair of nice cross country ski boots, but the insides are full of fuzzy mold! How can I clean/repair them?
Use 1 cup of vinegar and 1/2 cup of water.
Use a scrub brush to scrub away as much mold as you can.
Wipe out boots with a cloth until it is all gone.
Repeat steps if you have to.
Dry with a towel and set in the sun.
I would try the vinegar treatment above. If it should return, I would use some bleach.
I went on a missions trip to Louisiana years ago and they sprayed a bleach/water solution on the mold.
You can clean these boots with a solution of bleach and water.
I've used diluted bleach, rinse, and air dry in the sun for a small bag of similar fabrics. It worked well.