# SiteCheck Subdomain Takeover Monitor

> 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

## Facts

- Endpoint: GET https://api.fadeandco.workers.dev/api/agent-intel/subdomain-takeover-monitor?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sitecheck-subdomain-takeover-monitor-ba2fde04
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_b2WTApQjqojDere51MAaO

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability sitecheck-subdomain-takeover-monitor-ba2fde04
```

Example prompt: Can you check example.org for any subdomains that might be vulnerable to takeover — like unclaimed GitHub Pages, S3 buckets, or Heroku apps?

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "domain"
     ],
     "properties": {
      "domain": {
       "type": "string",
       "description": "Domain such as example.org (a URL is reduced to its host)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "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
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sitecheck-subdomain-takeover-monitor-ba2fde04/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.fadeandco.workers.dev](https://www.zero.xyz/host/api.fadeandco.workers.dev/llms.txt)