code: function getHbsCompatibleFilter (filterName) {
      var specialReturnValue = filterName === 'yavu' ? '\uFFFD' : '';
      return function filter (s) {
          // align with Handlebars preference to return '' when s is null/undefined, except in unquoted attr, '\uFFFD' is returned to avoid context breaking
          return s === null || s === undefined ? specialReturnValue : 
              // Unlike escapeExpression(), return s instead of s.toHTML() since downstream
              //  filters of the same chain has to be disabled too.
              //  Handlebars will invoke SafeString.toString() at last during data binding
              s.toHTML ? s : xssFilters._privFilters[filterName](s);
      };
  }
docs: don't escape SafeStrings, since they're already safe according to Handlebars Reference: https://github.com/wycats/handlebars.js/blob/master/lib/handlebars/utils.js#L63-L82