subdomain-takeover-check SKILL.md skillA
subdomain-takeover-check from dreadnode/capabilities is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add dreadnode/capabilities/subdomain-takeover-check@git:20260529.0ab6ab0Pins git:20260529.0ab6ab0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- dreadnode/capabilities
- Path
capabilities/web-security/skills/subdomain-takeover-check/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260529.0ab6ab0, committed May 29, 2026
- First version recorded
- May 4, 2026
- Size
- 2,285 bytes
- Repository stars
- 22
- License
- MIT
Ground-truth subdomain takeover candidates by checking CNAME resolution, verifying service availability, and validating fingerprint matches against can-i-take-over-xyz before reporting. Use when an agent or scanner flags a potential subdomain takeover, dangling CNAME, or unclaimed cloud resource.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Subdomain Takeover Ground-Truth Check Validates subdomain takeover candidates against the canonical [can-i-take-over-xyz](https://github.com/EdOverflow/can-i-take-over-xyz) service registry. ## Procedure 1. **Resolve DNS** — identify the target service: ```bash dig CNAME <subdomain> +short ``` If no CNAME is returned, check for A/AAAA records with `dig A <subdomain> +short`. No DNS resolution at all suggests the record was already cleaned up — flag as INVESTIGATE but note DNS is clean. 2. **Fetch the registry** — pull the raw README and find the service row: ```bash curl -s https://raw.githubusercontent.com/EdOverflow/can-i-take-over-xyz/master/README.md | rg -i "<service_name>" ``` If the registry fetch fails (network error, 404), note it and proceed with manual assessment. 3. **Check status** — is the service listed as `Vulnerable`, `Not Vulnerable`, or `Edge Case`? 4. **Match fingerprint** — fetch the subdomain and check for the documented fingerprint: ```bash curl -skL "https://<subdomain>" -o /tmp/takeover_body.txt 2>/dev/null rg -c "NoSuchBucket\|There isn't a GitHub Pages site here\|This page is reserved" /tmp/takeover_body.txt …
Read the whole file at its exact version.
How to install
mdr add dreadnode/capabilities/subdomain-takeover-check@sha256:9b89a3b880d7f9f4The line at the top of this page pins the label git:20260529.0ab6ab0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_6d54jnwemeyzokl5)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between May 4, 2026 and May 29, 2026, about one every 25 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260529.0ab6ab0 latest | 2026-05-29 | 0ab6ab0 | 2,285 B | A | view · diff |
| git:20260504.2a64374 | 2026-05-04 | 2a64374 | 1,677 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (2285 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
dreadnode/capabilities · 22 stars · license MIT · pushed 2026-11-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_6d54jnwemeyzokl5 GET https://markdownregistry.com/api/v1/resolve?ref=dreadnode/capabilities/subdomain-takeover-check GET https://markdownregistry.com/api/v1/blob/9b89a3b880d7f9f4608a941b10b216259e8098dac3792d16df3547868d5053ae
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.