Agent skill

Hunt Shadow API

by sickn33 in sickn33/agentic-awesome-skills

Hunt shadow / zombie / undocumented API surface (OWASP API9 Improper Inventory Management)

MITAuto-check passedSecurity

Install Hunt Shadow API

skills CLI
$ npx skills add sickn33/agentic-awesome-skills --skill hunt-shadow-api -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install sickn33/agentic-awesome-skills hunt-shadow-api --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/sickn33/agentic-awesome-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/hunt-shadow-api .claude/skills/hunt-shadow-api && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
hunt-shadow-api
GitHub stars
47k
Used in
1 other repo
Token cost
~2.5k tokens
SKILL.md length
1,008 words
Files
1
Skills in repo
1,394
Repo updated
First seen
Licence
MIT

At a glance

Hunt shadow / zombie / undocumented API surface (OWASP API9 Improper Inventory Management)

  • Works in 4 steps: Enumerate the Full Version Surface → Pull Every Reachable Spec, Not Just the… → Behavioral Diff Between Old and Current… → …
  • Tasks that involve Web application vulnerabilities
  • SKILL.md covers OWASP API9 — Improper…, Stage 1 — Enumerate the Full…, Stage 2 — Pull Every Reachable… and Stage 3 — Behavioral Diff…, plus 6 more sections
  • Calls curl and jq; reaches web.archive.org; needs EXPIRED_TOKEN

What it does

Hunt Shadow API is an agent skill from sickn33/agentic-awesome-skills. Hunt shadow / zombie / undocumented API surface (OWASP API9 Improper Inventory Management)

Its SKILL.md is about 2.5k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts. Compatibility notes: Requires explicit written authorization for a target scope plus the relevant testing tools for this technique. Docs-only; helper scripts and commands not…

It sits in Security, covering Web application vulnerabilities. The repository describes itself as: AAS Core is the local, agent-first control plane for complete catalog discovery, agent-owned selection, stack validation, and planning, backed by 2,400+ agentic skills. Includes… The licence is MIT.

When your agent uses it

  • Tasks that involve Web application vulnerabilities

Example prompts

  • “/hunt-shadow-api”

Requirements

  • A credential in EXPIRED_TOKEN
  • Compatibility (from SKILL.md): Requires explicit written authorization for a target scope plus the relevant testing tools for this technique. Docs-only; helper scripts and commands not bundled.

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. Enumerate the Full Version Surface
  2. Pull Every Reachable Spec, Not Just the Linked One
  3. Behavioral Diff Between Old and Current Version
  4. Deprecated / Internal Routes Never Referenced by the Current UI

What it can do on your machine

Read from SKILL.md and the folder at commit 1e53ce2. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • curl
    • jq

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Hosts in commands or code, which the agent is likely to contact:

    • web.archive.org

    Also links to:

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names these keys or tokens, usually read from environment variables:

    • EXPIRED_TOKEN

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Requires explicit written authorization for a target scope plus the relevant testing tools for this technique. Docs-only; helper scripts and commands not bundled.

    From compatibility in the SKILL.md frontmatter.

Context cost

Hunt Shadow API loads about 2.5k tokens when it runs. Until then it costs about 27 tokens; SKILL.md has 1,008 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~27
When it runs · the whole SKILL.md, loaded when a task matches
~2.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from sickn33/agentic-awesome-skills at commit 1e53ce2, republished under its MIT licence (© sickn33). 1,008 words, ~2,515 tokens.

Download SKILL.mdSave it as .claude/skills/hunt-shadow-api/SKILL.md (or your agent's skills folder).
name
hunt-shadow-api
description
Hunt shadow / zombie / undocumented API surface (OWASP API9 Improper Inventory Management)
compatibility
Requires explicit written authorization for a target scope plus the relevant testing tools for this technique. Docs-only; helper scripts and commands not bundled.
category
security
risk
offensive
source
https://github.com/elementalsouls/Claude-BugHunter
source_repo
elementalsouls/Claude-BugHunter
source_type
community
date_added
2026-09-20
license
MIT
license_source
https://github.com/elementalsouls/Claude-BugHunter/blob/main/LICENSE
sources
owasp_api_top10_2023, portswigger_research, public_research
report_count
0

⚠️ AUTHORIZED USE ONLY This skill is for educational purposes or authorized security assessments only. You must have explicit, written permission from the system owner before using this tool. Misuse of this tool is illegal and strictly prohibited.

Mandatory confirmation gate Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:

  1. Ask the user to state the exact target URL, IP, account, or resource.
  2. Ask the user to confirm written authorization and the permitted scope.
  3. Show the exact command(s) and explain their expected effect.
  4. Wait for explicit confirmation in the current conversation.

Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.

OWASP API9 — Improper Inventory Management (Shadow / Zombie APIs)

As an API evolves, old versions and internal/staging routes routinely stay reachable without receiving the same security fixes as the current version — because nobody tracks that they still exist. The bug is rarely in one endpoint; it's in the delta between what an old version enforces and what the current version enforces on the same operation.

When to use

Trigger when:

  • Versioned paths are visible (/v1/, /v2/, /api/2023-01-01/) or Accept/X-API-Version headers are in play.
  • A changelog, release notes, or deprecation notice references removed/old API behavior.
  • A mobile APK/IPA (via apk-redteam-pipeline / ios-redteam-pipeline) hardcodes endpoints that look like an older backend version than the current web app calls.
  • Multiple OpenAPI/Swagger specs are discoverable, or info.version in one spec implies others exist.

DO NOT use for single-version APIs with no version history — there's nothing to diff; go straight to hunt-api-misconfig for direct exploitation of the one surface that exists.


Stage 1 — Enumerate the Full Version Surface

bash
# Path-based versioning
for v in v1 v2 v3 v4 beta alpha internal legacy old 2022-01-01 2023-01-01 2024-01-01; do
  curl -s -o /dev/null -w "%{http_code} /api/$v/\n" "https://$TARGET/api/$v/"
done

# Header-based versioning
curl -s -H "X-API-Version: 1" https://$TARGET/api/users
curl -s -H "Accept: application/vnd.company.v1+json" https://$TARGET/api/users

# Subdomain-based versioning
for sub in api api-v1 api-v2 apiv1 apiv2 legacy-api old-api internal-api staging-api; do
  curl -s -o /dev/null -w "%{http_code} $sub\n" "https://$sub.$TARGET/"
done

A 200/401/403 on an old version path (anything but 404/connection-refused) means the version is still live and worth carrying into Stage 3, even if it demands auth.


Stage 2 — Pull Every Reachable Spec, Not Just the Linked One

bash
for path in openapi.json swagger.json v1/swagger.json v2/swagger.json v3/api-docs \
            api-docs.json swagger/v1/swagger.json .well-known/openapi.json; do
  curl -s -o /dev/null -w "%{http_code} /$path\n" "https://$TARGET/$path"
done

# Wayback Machine — a DEPRECATED version's spec often stays indexed after the live link is removed
curl -s "http://web.archive.org/cdx/search/cdx?url=$TARGET/*swagger*&output=json&collapse=urlkey"
curl -s "http://web.archive.org/cdx/search/cdx?url=$TARGET/*openapi*&output=json&collapse=urlkey"

When more than one spec resolves (a current one and an archived/old one), diff the endpoint inventories directly:

bash
jq -r '.paths | keys[]' v1-swagger.json | sort > /tmp/v1_paths.txt
jq -r '.paths | keys[]' v2-swagger.json | sort > /tmp/v2_paths.txt
comm -23 /tmp/v1_paths.txt /tmp/v2_paths.txt   # in v1 only — candidates for "still live but forgotten"

For every path in that diff, confirm it's still reachable against the v1 base URL. A route documented only in the old spec that still returns something other than 404 is a zombie- endpoint candidate — carry it into Stage 3.


Stage 3 — Behavioral Diff Between Old and Current Version

For each operation that exists in both versions, compare security-relevant behavior, not response shape. Response shape differences are Informational; behavioral security regressions are the finding.

  • Auth strength. Does the old version accept no token, an expired token, or a lower- privilege token that the current version rejects?
    bash
    curl -s -H "Authorization: Bearer $EXPIRED_TOKEN" https://$TARGET/api/v1/users/me -w '\n%{http_code}\n'
    curl -s -H "Authorization: Bearer $EXPIRED_TOKEN" https://$TARGET/api/v2/users/me -w '\n%{http_code}\n'
  • Rate limiting. Burst the same number of requests against both versions' equivalent endpoint; a missing 429 on the old version means rate-limiting was added later and never backported.
  • Input validation. Send the identical injection/oversized/malformed payload to both; the old version accepting what the new one rejects means hardening happened forward-only — chain into whichever injection class the payload targets (hunt-sqli, hunt-idor, etc.).
  • Field exposure. Does the old version's response body include fields — internal IDs, other users' data, internal notes, PII — that the current version has since redacted?

Stage 4 — Deprecated / Internal Routes Never Referenced by the Current UI

  • Grep JS bundles for API calls no visible UI flow triggers (/internal/, /admin/, /debug/, /_internal/, /test/, /staging/) — reuse hunt-source-leak's JS-bundle grep patterns for this specifically.
  • Check robots.txt / sitemap.xml for disallowed API paths — a self-inflicted disclosure.
  • Mobile-app endpoint inventories (via apk-redteam-pipeline / ios-redteam-pipeline) very often reference an older backend version than the current web app calls. Treat every APK/IPA-sourced endpoint as a version-diff candidate against the live web API.

Show full SKILL.md (408 more words)Show less

False-Positive Gate

  • A version difference alone (different response shape, cosmetic field renaming) is Informational. The finding is a security-relevant regression — auth, rate-limit, or validation that got weaker going backward in version history.
  • Confirm the old endpoint is not simply an alias/proxy to the current implementation before claiming a behavioral difference — send a payload that would actually behave differently under old vs. new logic, not just compare a version string in the response body.
  • A 200 on a path that just serves a static "this API version is deprecated, use v2" message is not a finding — confirm the underlying operation still executes.

Severity Table

FindingSeverity
Old version bypasses auth entirely where current version requires itCritical
Old version missing rate-limit present on current versionMedium–High (chain via hunt-brute-force)
Old version leaks extra fields (PII, internal IDs) vs. currentMedium–High
Old version accepts payloads the current version now validates/sanitizesHigh (chain to the underlying injection class)
Version is reachable but behaviorally identical to currentInformational

  • hunt-api-misconfig — owns exploitation once a spec or endpoint is in hand (mass assignment, JWT attacks, OData, Swagger-chain attacks). This skill hands it a sharper target: "here's a zombie endpoint with weaker validation than the current one."
  • hunt-subdomain — owns host/subdomain-level discovery (api-v1.target.com as its own host, potential takeover). This skill owns what happens once you're inside a given host's version surface.
  • hunt-source-leak — JS-bundle grep for internal/undocumented calls; reused here specifically for version-diffing rather than secret extraction.
  • apk-redteam-pipeline / ios-redteam-pipeline — mobile builds routinely hardcode an older API version; every mobile-sourced endpoint is a version-diff candidate.
  • hunt-brute-force — a rate-limit regression found here is only a complete finding once chained to actual brute-forceable impact (login, OTP, enumeration).

When to Use

  • You have explicit, written authorization to assess the target in scope, and the task matches this skill's vulnerability class or technique within a bug-bounty or penetration-test engagement.
  • You need the recon, exploitation, or validation workflow described below — executed strictly inside the approved scope.

Limitations

  • Authorized scope only: the confirmation gate above is mandatory before any probing, exploitation, or credential-access command.
  • Docs-only import: upstream helper scripts, commands, engine, and research assets are not bundled; reinstall tooling from the source repo when needed.
  • Validate every finding (see triage-validation) before reporting; report via report-writing. Prefer a sandbox, disposable VM, or controlled lab.
Example
bash
# Read-only first step; confirm scope before anything active.
cat scope.txt  # target list from the authorized engagement brief

Adapted from elementalsouls/Claude-BugHunter (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: executable helpers, commands, engine, and research assets not bundled.

© sickn33, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/hunt-shadow-api of sickn33/agentic-awesome-skills.

Open the folder on GitHubat commit 1e53ce2

Used in 1 other repository

We found 5 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in sickn33/agentic-awesome-skills, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Hunt Shadow API next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Hunt Shadow API compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Hunt Shadow API this skillsickn33/agentic-awesome-skills47k1 repos~2.5kAutomated safety check: PassMIT
Security And Hardeningpenpot/penpot61k6 repos~4.7kAutomated safety check: NotesMPL-2.0
Security Auditoreigent-ai/eigent15k—~1.8kAutomated safety check: NotesApache-2.0
Security Reviewjewbetcha/opentrace11617 repos~3.1kAutomated safety check: NotesMIT
Strix Code Vulnerability Scanusestrix/strix67k—~1.1kAutomated safety check: PassApache-2.0
Code Audit3stoneBrother/code-audit8931 repos~2.7kAutomated safety check: PassNone

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Categories

Questions about Hunt Shadow API

What does Hunt Shadow API do?

Hunt shadow / zombie / undocumented API surface (OWASP API9 Improper Inventory Management). Hunt Shadow API is an agent skill from sickn33/agentic-awesome-skills.

When should I use Hunt Shadow API?

Hunt Shadow API fits situations like: tasks that involve Web application vulnerabilities.

How do I install Hunt Shadow API in Claude Code?

Run `npx skills add sickn33/agentic-awesome-skills --skill hunt-shadow-api -a claude-code`. Or copy the skill folder (skills/hunt-shadow-api in sickn33/agentic-awesome-skills) into .claude/skills/hunt-shadow-api in your project. Claude Code loads it when a task matches its description.

How do I install Hunt Shadow API in Codex?

Run `npx skills add sickn33/agentic-awesome-skills --skill hunt-shadow-api -a codex`. Or copy the skill folder (skills/hunt-shadow-api in sickn33/agentic-awesome-skills) into .agents/skills/hunt-shadow-api in your project. Codex loads it when a task matches its description.

Can I use Hunt Shadow API in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add sickn33/agentic-awesome-skills --skill hunt-shadow-api -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/hunt-shadow-api, .gemini/skills/hunt-shadow-api, .github/skills/hunt-shadow-api and .opencode/skills/hunt-shadow-api in your project.

What does Hunt Shadow API need to run?

Going by SKILL.md and its folder, Hunt Shadow API needs the command-line tools its instructions call (curl and jq) and credentials named EXPIRED_TOKEN. Our summary lists: A credential in EXPIRED_TOKEN. Compatibility (from SKILL.md): Requires explicit written authorization for a target scope plus the relevant testing tools for this technique. Docs-only; helper scripts and commands not bundled..

Does Hunt Shadow API access the network?

SKILL.md names 2 domains. In commands or code: web.archive.org; the agent is likely to contact it when it follows the instructions. As links in the text: github.com. This is read from the text; nothing was executed.

Is Hunt Shadow API safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Hunt Shadow API use?

Hunt Shadow API is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Hunt Shadow API use?

About 2.5k tokens (SKILL.md is roughly 10k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Hunt Shadow API?

Skills that share tags, products or a category with Hunt Shadow API: Security And Hardening (penpot/penpot, 61k stars), Security Auditor (eigent-ai/eigent, 15k stars), Security Review (jewbetcha/opentrace, 116 stars) and Strix Code Vulnerability Scan (usestrix/strix, 67k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Hunt Shadow API?

sickn33 (a GitHub user) maintains it in sickn33/agentic-awesome-skills, which has 47,304 GitHub stars. The repository holds 1,394 skills in this directory. The repository was last updated on October 6, 2026.

Source: sickn33/agentic-awesome-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.