Two Resets Win
A07 · ≈ 45 min · 0 solves
Explore the application as a real target: map the exposed functionality, inspect requests and responses, build a working exploit, and recover the rotating flag. If you get stuck, the verified official solution is available below as an optional spoiler.
Rules of engagement
Stay inside the generated lab URL. Use only the synthetic accounts and data in this instance. The main SecOne4all site and external systems are out of scope.
Challenge brief
What counts as a valid solve
Two concurrent reset submissions both succeed because token consumption is not atomic.
POST /reset/race.
reach the protected synthetic account state without completing the intended authentication boundary; the successful workflow returns the current rotating flag.
Work only inside your generated lab URL and submit the flag within 45 minutes.
Official solution
Contains the complete exploitation path. Open it only when you want the spoiler.
Reveal official solutionStep-by-step · verified against the live lab
Official solution · A07 · Two Resets Win
Objective
Two concurrent reset submissions both succeed because token consumption is not atomic.
Steps
- Start the isolated lab and inspect the advertised authentication or recovery entry point.
- Complete the normal first step to obtain the synthetic session, token, or account state.
- Exploit the authentication failure: Send exactly two concurrent POST requests to
/reset/racewith the same one-time token. - Confirm the bypassed identity boundary returns the rotating instance flag.
- Submit the exact flag before stopping the lab.
Expected proof
A successful response for concurrent-reset-token returns the instance-specific rotating flag. The flag is valid only for the current player and running instance.
Safety boundary
Use only the generated lab URL. No request to the main site, another user, or an external service is part of this solution.