Downgrade Ticket
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
Force a protocol negotiation fallback that disables message protection.
POST /api/device/enroll, then POST /1.
recover a protected value or produce an accepted synthetic forgery through the application service; the successful workflow returns the current rotating flag.
Work only inside your generated lab URL and submit the flag within 45 minutes.
Official solution
Opening the walkthrough before solving permanently sets this lab's solve reward to 10 points.