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 woohyun212/security-skill --skill subdomain-takeovergit clone --depth 1 https://github.com/woohyun212/security-skillWrote 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/woohyun212/security-skill/subdomain-takeover)<a href="https://agentmods.dev/skills/woohyun212/security-skill/subdomain-takeover"><img src="https://agentmods.dev/badge/skills/woohyun212/security-skill/subdomain-takeover/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/woohyun212/security-skill/subdomain-takeover"><img src="https://agentmods.dev/badge/skills/woohyun212/security-skill/subdomain-takeover.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00016 | $0.03471 |
| Opus 5 | $0.00008 | $0.01736 |
| Sonnet 5 | $0.00003 | $0.00694 |
| Haiku 4.5 | $0.00002 | $0.00347 |
Grade A, and why
subdomain-takeover scanned grade A with 1 finding 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 9d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- `curl` installed How it starts
The opening of the file, as written. The whole thing — 295 lines — stays where its author put it; the contents beside it link to each section on GitHub.
What this skill does
Detects and verifies subdomain takeover vulnerabilities by identifying dangling DNS CNAME records that point to unclaimed or deprovisioned third-party services. For each CNAME, resolves the target, checks the HTTP response against known vulnerable-service fingerprints, and confirms exploitability by verifying the resource can be claimed. Covers 18+ vulnerable services including GitHub Pages, AWS S3, Heroku, Netlify, Azure (Traffic Manager, Blob, CloudApp), Shopify, Fastly, Ghost, Pantheon, Tumblr, WordPress.com, Cargo Collective, Surge.sh, Bitbucket, Zendesk, Readme.io, and Statuspage.
When to use
- During recon on a bug bounty program to find high-impact, low-effort findings
- After subdomain enumeration (e.g. from the
subdomain-enumskill) to check each live CNAME - When auditing an organization's DNS records for hygiene and dangling entries
- After a product decommissioning or cloud migration to verify DNS cleanup was complete
Prerequisites
diginstalled (part ofdnsutilson Debian/Ubuntu,bind-utilson RHEL/CentOS):apt install dnsutils # Debian/Ubuntucurlinstalledhttpxinstalled (for bulk HTTP probing):go install -v github.com/projectdiscovery/httpx/cmd/httpx@latest- One of the following automated scanners (choose one):
- subjack:
go install github.com/haccer/subjack@latest - nuclei with takeover templates:
go install -v github.com/projectdiscovery/nuclei/v3/cmd/nuclei@latest nuclei -update-templates
- subjack:
- Environment variable
SECSKILL_TARGET_DOMAIN: target root domain - Environment variable
SECSKILL_SUBDOMAIN_LIST: path to a file of subdomains (one per line); can be output from thesubdomain-enumskill
Inputs
| Variable | Required | Description |
|---|---|---|
SECSKILL_SUBDOMAIN_LIST |
required | Path to file containing subdomains to check (one per line) |
SECSKILL_TARGET_DOMAIN |
required | Root domain (used for labeling output files) |
SECSKILL_OUTPUT_DIR |
optional | Directory to save results (default: ./output) |
SECSKILL_USE_SUBJACK |
optional | Set to true to run subjack (default: false) |
SECSKILL_USE_NUCLEI |
optional | Set to true to run nuclei takeover templates (default: false) |
What ships with it
1 file 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.
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.
- 9d ago First seen · 295 lines · 16 tokens per session scan A e75ea71c354d
subdomain-takeover is a skill published in the GitHub repository woohyun212/security-skill (21 stars, last pushed 4mo ago), licensed MIT. It adds 16 tokens to every session and 3,471 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
systematic-debugging
Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.
local-ai-agents
Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…
next-cache-components-adoption
Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…
insight-error-page
Write or audit an insight-kind error page for the Next.js dev overlay. Use when creating a new errors/ .mdx page, auditing an existing one, or checking that a page matches the framework fix cards. Covers page structure, title alignment, FixCard cards with Copy prompt button, code snippets, terminology verification…
next-cache-components-optimizer
Drive a Next.js route to instant navigation by setting up an agentic loop, under Cache Components / PPR, on initial load (hard navigation) and client-side navigation (soft navigation). Encode the goal as a failing @next/playwright instant() e2e and work it to green, one verified route at a time; the shipped test then…
next-partial-prefetching-adoption
Turn on Partial Prefetching in a Next.js app and work through the insights it surfaces. Use when the user wants to enable or adopt Partial Prefetching, flip the partialPrefetching flag, opt routes in with export const prefetch = 'partial', audit Link prefetch={true} behavior, preserve existing prefetched UI with…