Security fixes are applied to the current npm release of mcp-web-validator and the currently deployed hosted endpoint at https://web-validator-mcp.digestseo.com/mcp. Older npm versions are not supported; upgrade to the latest published version before reporting a problem that may already be fixed.
Do not open a public GitHub issue for a suspected vulnerability.
Use GitHub private vulnerability reporting. If that form is unavailable, email tomi.seregi99@gmail.com with the subject Security report: mcp-web-validator. Do not include secrets or unrelated personal data.
Include, where possible:
- the affected surface (local npm server, hosted Worker, website, or packaging metadata);
- the affected version, commit, endpoint, and tool name;
- reproducible steps or a minimal proof of concept;
- the expected and observed impact;
- any suggested mitigation; and
- whether the issue has been disclosed elsewhere.
Please avoid accessing data that is not yours, disrupting the public service, or including credentials or personal data in the report. We aim to acknowledge complete reports within three business days and will coordinate remediation and disclosure with the reporter.
The local stdio server runs with the permissions of the MCP client that launches it. Its documented features can read user-selected files, make outbound validation and link-check requests, open local files or public URLs in a headless browser, and write screenshot files. Users should review every sensitive tool call and run MCP clients with least privilege.
The hosted app cannot access local files. It can process raw HTML or CSS supplied by the user, fetch one authorized public HTML webpage for a focused audit, and perform a bounded sitemap-first same-origin public-site audit. That audit first fetches the seed page to lock the final public origin, then may retrieve robots.txt, eligible same-origin XML sitemap documents, and up to eight eligible same-origin public HTML pages per request. It rejects private or reserved addresses, credentialed URLs, custom ports, external sitemap entries, subdomains, and cross-origin redirects for the site audit. It does not authenticate, execute webpage JavaScript, recursively follow arbitrary HTML links, fetch arbitrary linked assets or stylesheets, or perform site-wide broken-link crawling. Supplied or fetched HTML validation payloads may be sent to the external Nu HTML Checker; focused authorized broken-link checks may contact eligible public link URLs. See the privacy policy for data-handling details.
The following are normally outside this project's vulnerability scope unless they expose a project-specific weakness:
- availability or behavior of third-party validation services;
- social-engineering reports without a technical vulnerability;
- automated scanner output without a reproducible impact; and
- denial-of-service testing against the production endpoint without prior written permission.