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security-headers-configuration

@secondsky/claude-skills
13
23

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 Skill

Shared

Installs to .agents/skills, used by Codex, Amp, Warp, Cursor, OpenCode, and more.

CodexAmp
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Personal

Available across projects.

$npx skills-installer add @secondsky/claude-skills/security-headers-configuration --client shared
Project

Writes to .agents/skills.

$npx skills-installer add @secondsky/claude-skills/security-headers-configuration -p --client shared
Note: Review the skill instructions before using it.

SKILL.md

name security-headers-configuration
description 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.
license MIT

Security 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