[Hint#1] Sticky bit is configured in the flag02 file.
[Hint#2] If you execute the flag02 file, You can see the upper result that includes value of USER environment variable.
[Hint#3] The flag02 file finally executes the commands contained in the buffer.
It also posted at : http://cysecguide.blogspot.com/2016/09/nebula-level02-hint.html