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A04 · Cryptographic Failures · Medium

Predictable Recovery

20POINTS
35MINUTES
0SOLVES
MISSIONDiscover the weakness independently

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

FLAG REQUIREMENTS

What counts as a valid solve

Goal

Reconstruct a password-reset token generated from predictable process state.

Required interaction

GET /api/reset/request?user={value}, then POST /api/reset/redeem.

Completion proof

recover a protected value or produce an accepted synthetic forgery through the application service; the successful workflow returns the current rotating flag.

Session rule

Work only inside your generated lab URL and submit the flag within 35 minutes.

VERIFIED WALKTHROUGH

Official solution

Opening the walkthrough before solving permanently sets this lab's solve reward to 10 points.