Security Headers Check

Security Headers Check

A-F grade of response headers per the OWASP Secure Headers Project, using only curl. No signup required.

Prerequisites

• curl

Trigger

• "Check the security headers on example.com"
• "Do I have HSTS configured correctly?"
• "Grade my site's headers"
• "Is my CSP safe?"

Workflow

1. Fetch headers from the final URL. Resolve redirects first so you grade the page users actually land on, then capture its headers:

   FINAL=$(curl -sIL -o /dev/null -m 15 -w '%{url_effective}' "https://$DOMAIN/")
   curl -sI -m 15 "$FINAL" >/tmp/headers.txt
   grep -iE '^(HTTP|content-security|strict-transport|x-frame|x-content-type|referrer-policy|permissions-policy|server|x-powered-by)' /tmp/headers.txt
   

   If the status is 405/501 the server rejects HEAD — refetch with curl -s -D /tmp/headers.txt -o /dev/null -m 15 "$FINAL" (GET, headers dumped, body discarded).

2. Score each of the 6 headers (1 point each, full config required for the point):

   • Content-Security-Policy — present; script-src (or default-src fallback) has no 'unsafe-inline' unless paired with a 'nonce-...'/'sha256-...' source (which nullifies it); no 'unsafe-eval'; no bare * in script-src/object-src. A CSP that whitelists everything scores 0 — it mitigates nothing.
   • Strict-Transport-Security — present; max-age ≥ 15552000 (180 days, the enforced floor here; 31536000 is the OWASP-recommended value); includeSubDomains present. preload is bonus credit, not required.
   • Frame protection — X-Frame-Options: DENY|SAMEORIGIN, OR CSP frame-ancestors (which supersedes it). Either earns the point; neither = clickjacking exposure.
   • X-Content-Type-Options — exactly nosniff.
   • Referrer-Policy — present with a strict value (strict-origin-when-cross-origin, no-referrer, same-origin). unsafe-url scores 0.
   • Permissions-Policy — present and restricting at least camera, microphone, geolocation.

3. Information disclosure (penalty, not a point): flag Server: values carrying a version string (e.g. nginx/1.18.0) and any X-Powered-By at all. Each disclosure drops the final grade by one step (max one drop) — version banners hand attackers a CVE shopping list.

4. Grade:

Then apply the disclosure penalty from step 3. State the pre- and post-penalty grade if they differ.

5. Honesty rules: grade only what the response shows. A CSP delivered via <meta> tag will not appear in headers — note "no header-level CSP; meta-tag CSP not checked by this probe" instead of asserting there is no CSP at all. Do not suggest changing anything on the server; report findings only.

Report

## Security Headers Report: [final URL]

**Grade: [A-F]** ([n]/6 headers, [disclosure penalty applied? yes/no]) — per OWASP Secure Headers Project

| Header                    | Value found (truncated) | Verdict |
|---------------------------|-------------------------|---------|
| Content-Security-Policy   | [...]                   | [pass/weak/missing] |
| Strict-Transport-Security | [...]                   | [pass/weak/missing] |
| Frame protection (XFO/CSP)| [...]                   | [pass/missing] |
| X-Content-Type-Options    | [...]                   | [pass/missing] |
| Referrer-Policy           | [...]                   | [pass/weak/missing] |
| Permissions-Policy        | [...]                   | [pass/missing] |
| Disclosure (Server/X-Powered-By) | [...]            | [clean/leaking] |

### Findings
1. [MISSING/WEAK/LEAK] [header] — [evidence value] — [attack class it leaves open]

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