ctf-skills is a collection of agent instructions for solving capture-the-flag security challenges, including web exploitation, binary vulnerabilities, cryptography, reverse engineering, forensics, and OSINT. It is intended for agents and people working through CTF problems, and its skills can be loaded into supported coding-agent workflows.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ljagiello/ctf-skills --skill ctf-writeupgit clone --depth 1 https://github.com/ljagiello/ctf-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ljagiello/ctf-skills/ctf-writeup)<a href="https://agentmods.dev/skills/ljagiello/ctf-skills/ctf-writeup"><img src="https://agentmods.dev/badge/skills/ljagiello/ctf-skills/ctf-writeup/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ljagiello/ctf-skills/ctf-writeup"><img src="https://agentmods.dev/badge/skills/ljagiello/ctf-skills/ctf-writeup.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00048 | $0.01136 |
| Opus 5.5 | $0.00019 | $0.00454 |
| Sonnet 5.5 | $0.00010 | $0.00227 |
| Haiku 4.5 | $0.00005 | $0.00114 |
Grade A, and why
ctf-writeup scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- ctf-writeup — 100% identical, 1 lines differ
How it starts
The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CTF Write-up Generator
Generate a standardized submission-style CTF writeup for a solved challenge.
Default behavior:
- During an active competition, optimize for speed, clarity, and reproducibility
- Keep writeups short enough that a teammate or organizer can validate the solve quickly
- Always produce a
submission-style writeup - Prefer one complete solve script from challenge data to final flag
Workflow
Step 1: Gather Information
Collect the following from the current session, challenge files, and user input:
- Challenge metadata — name, CTF event, category, difficulty, points, flag format
- Solution artifacts — exploit scripts, payloads, screenshots, command output
- Timeline — key steps taken, dead ends, pivots
# Scan for exploit scripts and artifacts
find . -name '*.py' -o -name '*.sh' -o -name 'exploit*' -o -name 'solve*' | head -20
# Check for flags in output files
grep -rniE '(flag|ctf|eno|htb|pico)\{' . 2>/dev/null
Step 2: Generate Write-up
Write the writeup file as writeup.md (or writeup-<challenge-name>.md) using the submission template below.
Templates
Submission Format
---
title: "<Challenge Name>"
ctf: "<CTF Event Name>"
date: YYYY-MM-DD
category: web|pwn|crypto|reverse|forensics|osint|malware|misc|ai-ml
difficulty: easy|medium|hard
points: <number>
flag_format: "flag{...}"
author: "<your name or team>"
---
# <Challenge Name>
## Summary
<1-2 sentences: what the challenge was and the core technique. Keep it direct.>
## Solution
### Step 1: <Action>
<Explain the key observation in 3-8 short lines. Keep it direct.>
\`\`\`python
<one complete solving script from provided challenge data to printing the final flag>
\`\`\`
### Step 2: <Action> (optional)
<Only add this when a second short step genuinely helps readability, such as separating the core observation from final verification.>
### Step 3: <Action> (optional)
<Use only if the challenge really needs it. Keep the total number of steps small.>
## Flag
\`\`\`
flag{example_flag_here}
\`\`\`
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday Changed · +1 lines 09633dc2d75f
- 1mo ago Changed f67169dc8287
- 1mo ago First seen · 140 lines · 48 tokens per session scan A e3f43f41e3b4
ctf-writeup is a skill published in the GitHub repository ljagiello/ctf-skills (3,549 stars, last pushed yesterday), licensed MIT. It adds 48 tokens to every session and 1,136 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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