未测试（目前无法测试），但您应该能够使用筛选器添加属性。。。类似于：

function test_sc($atts,$content) {
  // echo \'test_sc\';
  $atts = shortcode_atts(
      array(
              \'foo\' => \'no foo\',
              \'bar\' => \'default bar\',
      ), 
      $atts, 
      \'testsc\' 
  );

  // var_dump($atts);

}
add_shortcode(\'testsc\',\'test_sc\');

function test_shortcode_att_add($atts) {
  # this filter should only run once (first use on page)
  remove_filter(\'shortcode_atts_testsc\',\'test_shortcode_att_add\');
  $atts[\'xxx\'] = \'yyy\';
  return $atts;
}
add_filter(\'shortcode_atts_testsc\',\'test_shortcode_att_add\');