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SiteCheck Subdomain Takeover Monitor
x402
SiteCheck Subdomain Takeover Monitor is a paid API for AI agents from api.fadeandco.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-29).
Checks up to 10 subdomains (from certificate transparency logs) of a domain for known 'unclaimed service' fingerprints indicating potential subdomain takeover vulnerability
Price / call$0.002
Success—
StatusUnknown
How this service works
Subdomain takeover check: lists up to 10 subdomains seen in certificate transparency logs for a domain (Cert Spotter), fetches each over HTTPS, and flags pages that show a known 'unclaimed service' message (GitHub Pages, S3, Heroku, Fastly). Looks at the page text only, not DNS records, so it can miss dangling records that show no such message.
Output
Returns a JSON object with the domain checked, the source (Cert Spotter CT logs), a list of up to 10 subdomains each with host name, HTTP status code, detected service (e.g. GitHub Pages, S3, Heroku, Fastly, or null), and a verdict (OK or flagged as possible takeover). Also includes the timestamp of the check, total subdomains checked, and count of possible takeovers found. Note: only page-text fingerprinting is used, not DNS record inspection.
Example use cases
Pre-launch security audit
“Before we go live, can you scan acmecorp.com for any subdomains that might be sitting unclaimed on GitHub Pages, S3, Heroku, or Fastly? I want to make sure nothing can be hijacked.”
Bug bounty recon on target domain
“I'm doing a bug bounty on targetcompany.io — can you pull subdomains from certificate transparency logs and flag any that show signs of being takeover-vulnerable?”
Ongoing brand protection monitoring
“Check mybrand.com for subdomains that could be taken over by someone registering an unclaimed service — I want to know if anything is showing a 'page not found' or unclaimed message on Heroku or GitHub Pages.”
Technical details
Endpoint
GEThttps://api.fadeandco.workers.dev/api/agent-intel/subdomain-takeover-monitor?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need a quick, low-cost check of whether any subdomains of a domain are exposing known unclaimed-service fingerprints (GitHub Pages, S3, Heroku, Fastly), using real certificate transparency data. Prefer this over a full DNS audit when you want a fast page-text signal rather than comprehensive DNS record inspection. Best suited for security recon, bug bounty reconnaissance, brand protection, and pre-launch audits where speed matters and DNS-layer analysis is handled separately.
Side effects
- Domain not found in certificate transparency logs — returns empty results list
- Subdomains unreachable over HTTPS — HTTP errors recorded but page text cannot be checked
- Known unclaimed-service message not present even on vulnerable page — verdicted as OK (false negative)
- DNS dangling records that serve no HTTP content will be missed entirely
- More than 10 subdomains exist — only the first 10 from CT logs are checked
- Invalid or malformed domain input — API may return an error or unexpected results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"note": "Page-text check only; a page that is not one of the known messages is reported OK, which is not proof the DNS record is safe. Max 10 subdomains per call.",
"domain": "example.org",
"source": "https://api.certspotter.com/v1/issuances",
"results": [
{
"host": "www.example.org",
"service": null,
"verdict": "OK",
"httpStatus": 200
}
],
"checkedAt": "2026-10-23T09:35:22.841Z",
"checkedSubdomains": 1,
"possibleTakeovers": 0
}
}Tags
x402
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