[KevinH]

Perhaps, it would be easier to set it to its default of true and then screen out any local file access in AcceptNavigationRequest that is outside the target epub.

I really do not want to have to register my own url schemes just to filter out file:/// scheme urls from within a evil epub.

I will see if that is a workable approach. If not, we will have to go with our own custom Scheme handler as calibre does.