using dirsearch in ``http://172.17.18.69:20011/``
and you can get new path named ``/update``
access to url http://172.17.18.69:20011/update you can see request ``405 Method Not Allowed``
change reuqest from get to post and open it again you well see updated successfully in page then access again to main page ``/``
you can see new gallary added ``http://172.17.18.69:20011/gallery/John`` access and you will get flag