Level 7 is a simple webpage that doesn't seem to offer us any clues about a vulnerability. Let's click around those links a bit to see more.
Well, each of these links passes the name of the page to a PHP script, which seems to just stuff the contents of the file into the webpage. So, we should be able to change that URL parameter to whatever we want, in order to get the contents of the file containing the next password.
users.txt -- that was the name of the file used in previous levels. Nope... well, in the intro to the wargames, we were told: "All passwords are also stored in
/etc/natas_webpass/" so let's look in
/etc/natas_webpass/natas7. Got it!
In addition to the webserver being configured to control access to only the material you want public, the webapp needs to do the same. The mistake here was to blindly accept client input as a filename to read.