Bandit7
Website URL: http://overthewire.org/wargames/bandit/bandit7.html
Log in to the game server using credentials of bandit6 (see this for walkthrough for that level).

Reading through the OverTheWire webpage for bandit7, we see:
The password for the next level is stored somewhere on the server and has all of the following properties:
owned by user bandit7
owned by group bandit6
33 bytes in size
Well, things got a bit more complicated than the previous level. We don’t exactly know where the file is. We cannot use ls since most of the directory listings would be suppressed So, we need to find a way around this.
Instead, this time we will use the alternative find command.
find / -user bandit7 -group bandit6 -size 33c

Going through the output, we can see a lot of errors, let’s clean up the output a bit. We just need to redirect error output to somewhere else. A slight modification to the previous command should do it.
find / -user bandit7 -group bandit6 -size 33c 2>/dev/null

Now, its a simple matter of getting the contents of the file using cat command.
cat /var/lib/dpkg/info/bandit7.password
We got the password for bandit7