Analyze HTTP security headers of web domains to identify vulnerabilities
SKILL.md
Analyzing Security Headers
Overview
Evaluate HTTP response headers for web applications against OWASP Secure Headers Project recommendations and browser security baselines. Identify missing, misconfigured, or information-leaking headers across both HTTP and HTTPS responses.
Prerequisites
Target URL or domain name accessible over the network
Authorization to perform HTTP requests against the target domain
Network connectivity for both HTTP and HTTPS protocols
Optional: write access to ${CLAUDE_SKILL_DIR}/security-reports/ for persisting results
Instructions
Accept the target domain. If only a domain name is provided, default to https://. For batch analysis, accept a newline-separated list.
Fetch response headers using WebFetch for both HTTP and HTTPS endpoints. Record the full redirect chain and final destination URL.
Evaluate critical headers -- flag any that are missing or misconfigured:
Strict-Transport-Security: require max-age>=31536000, includeSubDomains, and preload eligibility
Content-Security-Policy: check for unsafe-inline, unsafe-eval, overly broad default-src, and missing frame-ancestors
Check for information disclosure -- flag Server, X-Powered-By, X-AspNet-Version, and any header revealing technology stack or version numbers.
Inspect cookie attributes on Set-Cookie headers: verify Secure, HttpOnly, SameSite=Lax|Strict, and __Host-/__Secure- prefix usage.
Calculate a security grade: A+ (95-100), A (85-94), B (75-84), C (65-74), D (50-64), F (<50) based on weighted presence and correctness of each header.
Generate per-header remediation directives with configuration examples for Nginx, Apache, and Cloudflare.
See ${CLAUDE_SKILL_DIR}/references/implementation.md for the five-phase implementation workflow.
Output
Headers Analysis Report: overall grade, per-header status (present/missing/misconfigured), and risk impact
Remediation Checklist: prioritized fixes with server configuration snippets
Cookie Security Assessment: attribute compliance for each Set-Cookie header
Comparison Table: side-by-side HTTP vs. HTTPS header differences
Error Handling
Error
Cause
Solution
Failed to connect to domain
DNS resolution failure, firewall block, or domain down
Verify domain spelling and DNS records; test alternate protocols
SSL certificate verification failed
Expired, self-signed, or mismatched certificate
Note TLS issue in report; indicates HSTS not properly enforced
Too many redirects
Redirect loop between HTTP and HTTPS
Report the redirect chain and analyze headers at each hop
HTTP 429 Too Many Requests
Rate limiting by target server
Implement backoff; queue domain for delayed re-analysis
Headers differ between HTTP and HTTPS
Inconsistent server configuration
Report both sets; highlight critical differences and flag HSTS gap
Examples
"Analyze security headers for https://tonsofskills.com and explain any CSP or HSTS issues."
"Check headers for example.com on both HTTP and HTTPS and provide an Nginx remediation config."
"Batch-analyze headers for five staging domains and rank them by security grade."
