    def helper(self):
        if not self.cached_helper:
            cached_helper = self.formstyle(self.table,
                                           self.vars,
                                           self.errors,
                                           self.readonly,
                                           self.deletable)
            if self.csrf:
                cached_helper.append(INPUT(_type='hidden',_name='_formkey',
                                           _value=self.formkey))
            for key in self.hidden or {}:
                cached_helper.append(INPUT(_type='hidden',_name=key,
                                           _value=self.hidden[key]))
            self.cached_helper = cached_helper
        return cached_helper
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.