Is it necessary when wiping over the khuff that the water does not touch the foot?

If water reaches the foot due to holes in the khuff (leather slipper), then it is permissible to wipe over it as long as the tearing does not extend to more than the khuff. However, if water reaches the foot due to the thinness or lack of opacity of the khuff or sock, the majority of scholars stipulate their opacity. In contrast, Ibn Taymiyyah and some contemporary scholars permit wiping over them even if the skin of the foot is visible beneath them.