I haven't heard of them bothering bunnies but I have heard that they don't always have much effect on the fox either.
I would examine your hutch carefully, replace any twist type closures with proper bolts or hasp and staples with a padlock (I used these when I had small children to ensure bun wasn't accidentally left unlocked). Look at the wire, is it heavy gauge? Foxes can chew through chicken wire, is it well secured? It may need some extra nails or clips to strengthen its fixing - foxes tend to scratch and push at the wire at an edge or corner to gain entry.
When thinking about foxes remember they are as agile as a cat and as strong as a dog.
We have local foxes. I cover my hutches at night as even the sight of something nasty can be too much for a bunny. I use puppy panels to add an extra line of security fencing around the hutch and aviary.
We have a sensor garden light too, not that this deters the foxes but it tends to wake one of us up and we can more easily see if it's just a cat or something worse.
I will just add that the best deterent I have found is to chase him in my nightie, waving a swing ball bat! Didn't see him for a couple of months after that!
And don't forget most foxes are quite happy to be out and bout in the day now.