Eleven - CTF Challenge Writeup

Challenge Information

Name: Eleven
Category: Misc
Points: 10
Objective: Access and manipulate a custom Rubik’s Cube web challenge under restricted user sessions to retrieve the flag.

From User Ten, we’re given a custom web challenge.
At first, I couldn’t open the Rubiks.html file due to permission issues.
After 45 minutes of debugging, I realized I had been su-ing through multiple users — causing nested shells under User Zero’s terminal.
Because of that, although I was technically User Ten, the permission context was messed up.
To fix this, I logged out completely and logged in directly as User Ten. That allowed me to open Firefox and view the HTML page.
The challenge was a Rubik’s Cube simulation. As someone who can solve a cube physically, I considered solving it directly.
- But the page didn’t allow turning multiple layers, and I couldn’t mentally map 1-layer operations.
- So instead, I chose the easier way: modifying the source code to force the check function to always return true.
This trick worked — and the flag was revealed.

RUBIKSCUBEMASTA