code: function errorHandler(error, req, res, next) {
      req.body.email = '';
      req.body.subscribed_url = santizeUrl(req.body.subscribed_url);
      req.body.subscribed_referrer = santizeUrl(req.body.subscribed_referrer);
  
      if (error.statusCode !== 404) {
          res.locals.error = error;
          return _renderer(req, res);
      }
  
      next(error);
  }
docs: Takes care of sanitizing the email input.
  XSS prevention.
  For success cases, we don't have to worry, because then the input contained a valid email address.