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.