Security Headers Configuration Skill for Claude
Configures HTTP security headers to protect against XSS, clickjacking, and MIME sniffing attacks. Use when hardening web applications, passing security audits, or implementing Content Security Policy.
Install
one command, takes just this skill from the repositorynpx skills add https://github.com/secondsky/claude-skills --skill security-headers-configurationThe instruction itself
8 sections, as written by the authorSecurity Headers Configuration
Implement HTTP security headers to defend against common browser-based attacks.
Essential Headers
| Header | Purpose | Value |
|--------|---------|-------|
| HSTS | Force HTTPS | max-age=31536000; includeSubDomains |
| CSP | Restrict resources | default-src 'self' |
| X-Frame-Options | Prevent clickjacking | DENY |
| X-Content-Type-Options | Prevent MIME sniffing | nosniff |
Express Implementation
const helmet = require('helmet');
app.use(helmet());
// Custom CSP
app.use(helmet.contentSecurityPolicy({
directives: {
defaultSrc: ["'self'"],
scriptSrc: ["'self'", "'unsafe-inline'"],
styleSrc: ["'self'", "'unsafe-inline'"],
imgSrc: ["'self'", "data:", "https:"],
connectSrc: ["'self'", "https://api.example.com"],
fontSrc: ["'self'", "https://fonts.gstatic.com"],
frameAncestors: ["'none'"]
}
}));
Nginx Configuration
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
add_header X-Frame-Options "DENY" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header Referrer-Policy "strict-origin-when-cross-origin" always;
add_header Permissions-Policy "geolocation=(), microphone=(), camera=()" always;
add_header Content-Security-Policy "default-src 'self'; script-src 'self'" always;
Verification Tools
Security Headers Checklist
- [ ] HSTS enabled with long max-age
- [ ] CSP configured and tested
- [ ] X-Frame-Options set to DENY
- [ ] X-Content-Type-Options set to nosniff
- [ ] Referrer-Policy configured
- [ ] Permissions-Policy disables unused features
Additional Implementations
See references/python-apache.md for:
- Python Flask security headers middleware
- Flask-Talisman library configuration
- Apache .htaccess configuration
- Header testing script
Common Mistakes
- Setting CSP to report-only permanently
- Using overly permissive policies
- Forgetting to test after changes
- Not including all subdomains in HSTS
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How to use it
Take secondsky/security-headers-configuration from the repository into ~/.claude/skills for personal
use, or into .claude/skills inside a project.
The agent identifies a skill by the name field in its header. Two skills with the
same name cannot sit side by side — one of them will be ignored.