Bug in embedded documents

gistfile1.txt

{  
   "_id":{  
      "$oid":"54033bf96d627008c6000000"
   },
   "websites":[  
      {  
         "_id":{  
            "$oid":"54033bf96d627008c6010000"
         },
         "created_at":"2014-08-31T15:15:05.278Z",
         "posts":[  
            {  
               "_id":{  
                  "$oid":"54033bf96d627008c6020000"
               },
               "created_at":"2014-08-31T15:15:05.293Z",
               "images":[  
                  {  
                     "_id":{  
                        "$oid":"54033bf96d627008c6040000"
                     },
                     "created_at":"2014-08-31T15:15:05.296Z",
                     "updated_at":"2014-08-31T15:15:05.296Z"
                  },
                  {  
                     "_id":{  
                        "$oid":"54033bf96d627008c6050000"
                     },
                     "created_at":"2014-08-31T15:15:05.297Z",
                     "updated_at":"2014-08-31T15:15:05.297Z"
                  }
               ],
               "updated_at":"2014-08-31T15:15:05.293Z"
            },
            {  
               "_id":{  
                  "$oid":"54033bf96d627008c6030000"
               },
               "created_at":"2014-08-31T15:15:05.295Z",
               "updated_at":"2014-08-31T15:15:05.295Z"
            }
         ],
         "updated_at":"2014-08-31T15:15:05.278Z"
      }
   ]
}