Java ChallengeHow sharp is your Java? Prove it on the leaderboard.
One hour, a real box, and an auth check that lets the wrong people in. The best scores find the bug and fix it clean. Get a score out of 100, a tier, and your rank.
Free to play. Runs in your browser. Sign in to save and share your rank.
Tests green in 7m 10s. Spotted the reference compare fast.
The challenge
Close the hole
The admin check passes for the wrong input because it compares strings by reference. This is the actual console you get. Find the bug and get the tests green.
What we score
Outcome, root cause, restraint
Everyone gets the same broken project. The score is your judgement: did it come back to life, did you find the real cause, and was the fix clean.
Get it working
Outcome is graded first. A change that does not run is not a fix, however elegant it looks.
Find the real cause
We reward finding the actual root cause and fixing that, not patching the symptom and hoping.
Keep it clean
A minimal, correct change scores higher than a pile of guesses. Restraint counts.
The leaderboard
Where will you land?
Every run is judged on the same challenge, so the score is comparable. Climb from Learning to Elite, beat your friends, and share a link that shows exactly where you rank.
Claim your rankHow it works
Three steps, one hour, one rank
Boot the broken stack
A real Linux machine spins up in your browser with the broken project, an editor, and a terminal. Nothing to install.
Fix it yourself
You have an hour. Read the logs, find the real root cause, and make the smallest change that brings it back to life.
Get scored and ranked
When it is live, the judge scores your run out of 100, hands you a tier, and drops you on the leaderboard.
Find out how sharp your Java really is
One security hole, one hour, one shareable rank. No setup, no install. Start in your browser right now.
FAQ
Questions, answered
It is a hands-on challenge on a real Linux machine. You fix a subtle auth bug in a Java service and get its tests passing. You have up to an hour, and we score the outcome, whether you found the real root cause, and how clean your change was.
No. The whole challenge runs in your browser on a real Linux box with an editor and a terminal already set up. Nothing to download, nothing to configure.
You have up to an hour, but the highest scores finish fast and clean. It is free to play. Sign in to save your result and share it.
A shareable score out of 100, a tier, and your rank against everyone else who has taken it. Send the link to a friend and challenge them to beat it.