competition-stego-media

competition-stego-media is a skill for Codex from Asaiuta/reverse-workbench-skill. It costs 100 tokens per session (599 once invoked), scanned A, a copy of competition-stego-media, MIT.

A specialized guide for CTF exercises where information is hidden inside images, audio, video, documents, or other media files. Steganography means concealing data inside an otherwise ordinary file.

In plain words
What is it for?
Use it to find and reproduce hidden payloads in media containers, including data stored in alpha channels, color bits, video frames, document structure, or appended file content.
Why use it?
It provides a structured way to verify the real file format and inspect metadata, hidden channels, thumbnails, extra data, and encoding artifacts before guessing at deeper methods.

Skill for Codex

Written for Codex: agents/openai.yaml present. Also seen: $skill-name invocation.

Good fit Use it to find and reproduce hidden payloads in media containers, including data stored in alpha channels, color bits, video frames, document structure, or appended file content.

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Install with agentmods
npx agentmods add skills/asaiuta/reverse-workbench-skill/competition-stego-media
Install

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.

Any agent
npx skills add Asaiuta/reverse-workbench-skill --skill competition-stego-media
Clone the repo
git clone --depth 1 https://github.com/Asaiuta/reverse-workbench-skill

Made for: Codex.

Wrote 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.

agentmods badge for competition-stego-media

README.md
[![agentmods](https://agentmods.dev/badge/skills/asaiuta/reverse-workbench-skill/competition-stego-media/github.svg)](https://agentmods.dev/skills/asaiuta/reverse-workbench-skill/competition-stego-media)
Your own site
<a href="https://agentmods.dev/skills/asaiuta/reverse-workbench-skill/competition-stego-media"><img src="https://agentmods.dev/badge/skills/asaiuta/reverse-workbench-skill/competition-stego-media/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.

agentmods 80×15 button for competition-stego-media

Your own site · 80×15
<a href="https://agentmods.dev/skills/asaiuta/reverse-workbench-skill/competition-stego-media"><img src="https://agentmods.dev/badge/skills/asaiuta/reverse-workbench-skill/competition-stego-media.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 100 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 599 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00100 $0.00599
Opus 5 $0.00050 $0.00300
Sonnet 5 $0.00020 $0.00120
Haiku 4.5 $0.00010 $0.00060

Measured 10d ago against content hash 34c6ec0ebc77, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

competition-stego-media 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 10d ago.

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.

Origin

This is a copy

100% identical to competition-stego-media — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

CTF-Sandbox-Orchestrator/competition-stego-media/SKILL.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Competition Stego Media

Use this skill only as a downstream specialization after $ctf-sandbox-orchestrator is already active and has established sandbox assumptions, node ownership, and evidence priorities. If that has not happened yet, return to $ctf-sandbox-orchestrator first.

Use this skill when the challenge lives inside a media container, hidden channel, or appended payload rather than a conventional crypto blob.

Reply in Simplified Chinese unless the user explicitly requests English.

Quick Start

  1. Confirm the real container type, dimensions, duration, codec, and chunk layout before guessing a hidden layer.
  2. Check metadata, thumbnails, sidecar files, and appended trailers before deeper signal-domain work.
  3. Rank candidate channels by evidence: alpha, palette, LSB, transform-domain residue, frame order, or container slack.
  4. Preserve each extracted layer separately so the transform chain stays reproducible.
  5. Stop when the hidden payload is reproduced, not merely suspected.

Workflow

1. Establish Container Truth

  • Inspect headers, chunk tables, EXIF or document metadata, container indexes, thumbnails, and file size anomalies.
  • Compare declared format against observed structure to catch polyglots, appended archives, or malformed trailers.
  • Record exact offsets, frame numbers, or channel boundaries that look promising.

2. Inspect Candidate Channels

  • Check alpha, palette order, RGB or YUV planes, LSBs, spectrogram features, document object streams, or video frame deltas.
  • Prefer evidence-driven attempts over brute forcing every transform.
  • Note whether the payload is plain bytes, another media layer, compressed data, or an encrypted blob.

3. Reconstruct The Hidden Payload Path

  • Keep the chain in order: container -> channel or carrier -> extraction -> decompression or decode -> final parse.
  • Separate extraction success from final interpretation; a channel hit is not the same as artifact recovery.
  • If the problem becomes primarily about cryptography after extraction, hand off to the broader crypto skill.

Read the full file on GitHub · 51 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

  1. 10d ago First seen · 51 lines · 100 tokens per session scan A 34c6ec0ebc77

Subscribe to this mod's changes

competition-stego-media is a skill published in the GitHub repository Asaiuta/reverse-workbench-skill (2 stars, last pushed 27d ago), licensed MIT. It adds 100 tokens to every session and 599 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to competition-stego-media, differing in 0 lines, and is treated as a copy.

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