bool_t mqttSnClientIsShortTopicName(const char_t *topicName)
{
   bool_t res;

   //Initialize variable
   res = FALSE;

   //A short topic name is a topic name that has a fixed length of two octets
   if(osStrlen(topicName) == 2)
   {
      //Ensure the topic name does not contains wildcard characters
      if(strchr(topicName, '#') == NULL && strchr(topicName, '+') == NULL)
      {
         //The short topic name is a valid
         res = TRUE;
      }
   }

   //Return TRUE if the specified topic name is a short topic name
   return res;
}
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.