    def get_vars_next(self):
        next = current.request.vars._next
        if isinstance(next, (list, tuple)):
            next = next[0]
        if next and self.settings.prevent_open_redirect_attacks:
            return prevent_open_redirect(next)
        return next or None
A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.