Is the forum owner sinful if some members put pictures of women in their signatures, avatars, and personal images?

The authority and powers granted must be used to prevent the placement of forbidden images in members' signatures, and there should be no shyness in denouncing evil, for it is a religious obligation. Approving evil is forbidden. This is especially true for those who possess administrative authority. If it is impossible to regulate the forum according to religious guidelines, it must be closed.