October Season: Close the Door
Three boxes, three doors left open on the way out — a passwordless-root sudoers backdoor, a SUID-root shell in the weeds, and an SSH config wide open with a stranger's key in it. Find each foothold, close it without breaking the legitimate access around it, and recover what they left behind. Sandboxes you fully control. Defensive hardening only.
Archived season — playable for practice, no leaderboard points. Official write-ups are open.
The Rule They Left Behind
security · sudo · sudoers
SUID in the Weeds
security · suid · privilege-escalation
Close the Door
security · ssh · hardening
The Rule They Left Behind
150 pts · decays to 60 · +25 first bloodA departing contractor left the `deploy` service account a passwordless-root sudoers drop-in, disguised as leftover CI plumbing. Sudo policy is layered — `/etc/sudoers` plus every file in `/etc/sudoers.d/` — so the backdoor is one of the drop-ins. Remove it without breaking the legitimate `%wheel` admin grant, and recover the offboarding receipt (a dotfile in root's home). You have full root on this isolated box.
The live sandbox for this challenge isn't available yet — brief and hints are open.
Hints
Sudo policy is layered: /etc/sudoers plus every file in /etc/sudoers.d/. grep -rn deploy /etc/sudoers /etc/sudoers.d finds the backdoor.
Submit flag
Complete every objective in the lab and use Verify & grade, then submit the flag from that same box here.
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Archived — solves are for practice, not the leaderboard.
Season standings
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