Basic 9
From Kyle's Wiki
For this mission you -must- use directory transversal instead of the full path. Go back to basic 8 ( http://www.hackthissite.org/missions/basic/8/ ) and put this into the name box:
<!--#exec cmd="ls ../../9/" -->
You will then see your obscured file. Go to /missions/basic/9/TheFile.php to get your password.