Are you too lazy to ping websites? Then just use this convenient cloud service to ping sites for you!
http://forever.isss.io:4222
by mattyp
(attach app.py)
Based on the output or the source code, you might recognize that this webapp is
running the command line utility ping. In the source code, you can see that the
variable command is formed by directly concatenating user input with the ping
command. Thus, you can use different command line metacharacters to run other
commands. For instance, you could exploit the ; metacharacter by entering this:
google.com; echo hello
The flag is stored at /flag.txt. You just need to figure out how to read the file
by injecting a command!