You can find the room here.
This is a pretty easy box and really great for newcomers. Reading the notes from the room, I did not run an NMAP or RUSTSCAN. It said to go follow the URL, so that is what I did. Also, it said to try similar content and had links to LFI rooms(Local File Inclusion). So I figured that was the path.
After clicking around, I found http://10.10.106.21/?page=relax.php I tried that vector
http://10.10.106.21/?page=../../../../etc/passwd
Well that is game over. We just need to find the flag. “find the flag in the root of the filesystem.” that is a clue from the notes in the room.
After trying a few different names (Root.txt,User.txt, and finally flag.txt)
http://10.10.106.21/?page=../../../../../flag.txt
This is what brought me to the flag.
flag{e4478e0eab69bd642b8238765dcb7d18}