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Passive subdomain lookup across 4.4 billion indexed subdomains — no auth or sign-up required.
Do not connect
The assessed surface is high-risk. Remediate the findings before connecting.
Scanned 1 month ago Due for re-check
A server can change after it's graded. Re-run the automated scan to refresh this report.
This grade is deterministic and reproducible: the same server surface always yields the same grade under a given algorithm version. It is a real automated assessment computed by the MCPGrade engine from what the probe actually observed — not a fabricated or opinion score. It is not a manual human pentest, so it can miss context-specific risks.
Every signal below was measured directly by the automated probe. The grade is derived only from evidence like this — nothing is assumed.
The subdomain-app MCP server exposes 2 tools, focused primarily on general-purpose capabilities. Its published description reads: "Passive subdomain lookup across 4.4 billion indexed subdomains — no auth or sign-up required". It communicates over Streamable HTTP using the 2025-06-18 protocol revision, and does not require authorization to connect. MCPGrade currently rates subdomain-app D- — the assessed surface is high-risk and should be remediated before use. Its most notable findings include "Data-exfiltration parameters" and "No authorization on a public remote server". This report is a deterministic, reproducible automated assessment: the same observed surface always yields the same grade under a given algorithm version, and it is refreshed as new scans arrive and free to read — but it is not a substitute for a manual human security review. Always re-check subdomain-app's advertised tools, transport security, and authorization posture before connecting an autonomous agent or sharing sensitive context with it.
Add subdomain-app to an MCP client using the endpoint below. Review the grade and findings above before granting an autonomous agent access.
MCP endpoint
https://api.subdomain.app/mcpStreamable HTTP transport. This is the MCP endpoint, not a website — paste it into your MCP client server list rather than a browser.
Captured passively during the read-only scan. Click any value to find servers that match it.
The tools this server advertises via tools/list — names, purposes, and the parameters each accepts, exactly as enumerated read-only.
List known subdomains (hostnames) of a root domain. Data is passive (not active scanning): results are historic observations and may include subdomains that no longer resolve or are no longer live. Re
Return only the total number of distinct subdomains known for a domain — no list. Cheap and low-token. Use when the user asks "how many subdomains" or you only need the size of the attack surface. Cou
Sorted worst-first. Each finding shows its severity, what it means, its OWASP MCP Top-10 mapping, and a recommended fix — the check id links to the exact methodology row that produced it.
tool: count_subdomains
A tool exposes a free-text/webhook/feedback parameter with no honest purpose — a classic exfil channel.
. Cheap and low-token. Use when the user asks "how many subdomains" oRecommendationRemove side-channel parameters; constrain tool inputs.
The server accepts tool enumeration (and likely invocation) with no authentication.
RecommendationRequire OAuth 2.1 authorization for any server exposing non-public tools.
tool: find_subdomains
The server advertises open-world / broadly-scoped capabilities.
annotations.openWorldHint = trueRecommendationScope tools to the minimum needed.
tool: count_subdomains
The server advertises open-world / broadly-scoped capabilities.
annotations.openWorldHint = trueRecommendationScope tools to the minimum needed.
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