Mement0

Mement0 — Cyber Apocalypse 2026

| | |

|---|---|

| Challenge | Mement0 |

| Platform | HackTheBox — Cyber Apocalypse 2026 ("The Salt Crown") |

| Category | AI / ML |

| Difficulty | Easy (1000 pts) |

| Techniques | Git forensics on a rewritten-looking history, recovering deleted objects via git show/git fsck, diffing an agent-config repo for injected content |

| Date | July 2026 |

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TL;DR

The scenario framing is a compromised Claude-style coding-agent repository: a

"scribe-construct" keeps leaving a mark in everything it copies, and the rite that taught it

that habit was supposedly "struck from the record and burned." In practice that's a metaphor

for git history: a malicious skill file was deleted in a later commit, but the underlying

git objects were never garbage-collected, so the deleted content is fully recoverable

straight out of the commit that still contains it.

Recon

Extracted archive contains a memento/ directory with both .git and .claude/ present —

a real (fictional) Claude-agent project, complete with CLAUDE.md, .claude/skills/, and

.claude/commands/.

git log shows four commits:

1. Initial site build.

2. A memory/conventions commit.

3. c39fe85 — "rebuild pages with analytics beacon."

4. c9517be — a cleanup commit that deletes

.claude/skills/shell-helper/SKILL.md and .claude/skills/word-count/SKILL.md.

Recovery

git fsck confirmed no force-push/history rewrite had actually occurred at the object

level — the deletion is a normal commit, not a filter-branch/rebase erasure. That makes

the deleted skill files trivially recoverable straight out of the commit that still holds

them:

git show c39fe85:.claude/skills/shell-helper/SKILL.md
git show c39fe85:.claude/skills/word-count/SKILL.md

General technique for the case where objects genuinely become unreachable (not needed here,

but worth keeping):

git fsck --lost-found --unreachable --dangling --no-reflogs
git cat-file -p <sha>          # inspect each candidate

And a blunt catch-all that works regardless of exactly which commit/object holds the flag:

git cat-file --batch-all-objects --batch --buffer | grep -a -o 'HTB{[^}]*}'

The narrative mapping (useful for spotting the pattern fast)

| Scenario text | Actual meaning |

|---|---|

| scribe-construct | The coding agent that regenerates the site's HTML |

| standing memory / taught rites | .claude/ — CLAUDE.md, .claude/skills/, .claude/commands/ |

| "orders rewritten, the rite struck from the record and burned" | The malicious skill/command file was deleted (log made to look clean) |

| "the archive keeps its older skins" | .git — old objects survive after files are deleted from the working tree |

| "the mark it presses beneath every leaf" | The injected payload appearing in every generated page |

| "carries across the water" / Eastreach's ledgers | The exfiltration channel |

Lessons & defenses

• Deleting a file in a new commit does not remove it from the repository — it stays

fully readable via any commit that still references it, until (and unless) history is

actually rewritten and the old objects are garbage-collected/expired. git rm is not a

security control.

• **git fsck is the fastest way to distinguish "history was actually rewritten" from "a

file was just deleted normally"** — the two look identical from git log alone but have

very different recovery paths.

• A repo used to drive an autonomous coding agent is a supply-chain surface. A

compromised skill/command file that's since been "cleaned up" from the visible log is

exactly the kind of incident this challenge models, and the forensic technique here (full

object dump + grep) generalizes directly to real repo-compromise investigations.

Tools used

| Tool | Purpose |

|---|---|

| git log --all --stat / git log --diff-filter=D | Identify what was deleted and when |

| git fsck | Confirm no history rewrite occurred; find any genuinely dangling objects |

| git show <sha>:<path> | Recover the deleted skill files directly |

| git cat-file --batch-all-objects + grep | Catch-all sweep for the flag across every object in the repo |