What it tests:

Makes 10 consecutive requests to rate-limited endpoint
Verifies first 5 succeed (HTTP 200)
Verifies requests 6-10 are blocked (HTTP 429)
Tests rate limit reset after 60 seconds

Expected output:

Testing Rate Limiting (5 requests/minute per IP)
Request  1: ✓ 200 - Success
Request  2: ✓ 200 - Success
Request  3: ✓ 200 - Success
Request  4: ✓ 200 - Success
Request  5: ✓ 200 - Success
Request  6: ✗ 429 - Too many requests
Request  7: ✗ 429 - Too many requests
Request  8: ✗ 429 - Too many requests
Request  9: ✗ 429 - Too many requests
Request 10: ✗ 429 - Too many requests

✓ Rate limiting is working correctly!

Manual Testing

# Test rate limiting manually
for i in {1..10}; do
  echo "Request $i:"
  curl -s -o /dev/null -w "%{http_code}\n" \
    http://localhost:3000/api/test-rate-limit
  sleep 0.1
done

# Expected:
# Requests 1-5: 200
# Requests 6-10: 429

Test Reset After Window

# Make 5 requests
for i in {1..5}; do
  curl http://localhost:3000/api/test-rate-limit
done

# Wait 61 seconds (rate limit window = 60 seconds)
sleep 61

# Try again - should succeed
curl http://localhost:3000/api/test-rate-limit

# Expected: 200 OK (limit reset)

Testing CSRF Protection

Test 1: Request Without Token (Should Fail)

curl -X POST http://localhost:3000/api/example-protected \
  -H "Content-Type: application/json" \
  -d '{"title": "test"}'

# Expected: 403 Forbidden
# {
#   "error": "CSRF token missing"
# }

Test 2: Request With Valid Token (Should Succeed)

# Step 1: Get CSRF token
TOKEN=$(curl -s http://localhost:3000/api/csrf \
  -c cookies.txt | jq -r '.csrfToken')

# Step 2: Use token in request
curl -X POST http://localhost:3000/api/example-protected \
  -b cookies.txt \
  -H "Content-Type: application/json" \
  -H "X-CSRF-Token: $TOKEN" \
  -d '{"title": "test"}'

# Expected: 200 OK

Test 3: Token Reuse (Should Fail)

# Get token
TOKEN=$(curl -s http://localhost:3000/api/csrf \
  -c cookies.txt | jq -r '.csrfToken')

# Use once (succeeds)
curl -X POST http://localhost:3000/api/example-protected \
  -b cookies.txt \
  -H "X-CSRF-Token: $TOKEN" \
  -d '{"title": "test"}'

# Try to reuse same token (should fail)
curl -X POST http://localhost:3000/api/example-protected \
  -b cookies.txt \
  -H "X-CSRF-Token: $TOKEN" \
  -d '{"title": "test2"}'

# Expected: 403 Forbidden - Token already used

Test 4: Invalid Token (Should Fail)

curl -X POST http://localhost:3000/api/example-protected \
  -H "Content-Type: application/json" \
  -H "X-CSRF-Token: fake-token-12345" \
  -d '{"title": "test"}'

# Expected: 403 Forbidden
# {
#   "error": "CSRF token invalid"
# }

Testing Input Validation

Test XSS Sanitization

# Test script tags removal
curl -X POST http://localhost:3000/api/example-protected \
  -H "Content-Type: application/json" \
  -H "X-CSRF-Token: <get-token-first>" \
  -d '{"title": "<script>alert(1)</script>"}'

# Expected: 200 OK
# Title sanitized to: "alert(1)"
# < and > removed

Test Length Validation

# Test too-long input
curl -X POST http://localhost:3000/api/example-protected \
  -H "Content-Type: application/json" \
  -H "X-CSRF-Token: <token>" \
  -d "{\"title\": \"$(printf 'A%.0s' {1..200})\"}"

# Expected: 400 Bad Request
# {
#   "error": "Validation failed",
#   "details": {
#     "title": "String must contain at most 100 character(s)"
#   }
# }

Test Email Validation

curl -X POST http://localhost:3000/api/contact \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Test User",
    "email": "not-an-email",
    "subject": "Test",
    "message": "Test message"
  }'

# Expected: 400 Bad Request
# {
#   "error": "Validation failed",
#   "details": {
#     "email": "Invalid email"
#   }
# }

Test Required Fields

curl -X POST http://localhost:3000/api/contact \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Test User"
  }'

# Expected: 400 Bad Request with missing field errors

Testing Security Headers

Test All Headers

curl -I http://localhost:3000

# Expected headers:
# Content-Security-Policy: default-src 'self'; ...
# X-Frame-Options: DENY
# X-Content-Type-Options: nosniff
# (HSTS only in production)

Test CSP

# Check CSP includes required domains
curl -I http://localhost:3000 | grep "Content-Security-Policy"

# Should include:
# - script-src with Clerk domain
# - connect-src with Convex domain
# - frame-src with Stripe domain

Test HSTS (Production Only)

# In production environment
curl -I https://yourapp.com | grep "Strict-Transport-Security"

# Should return:
# Strict-Transport-Security: max-age=31536000; includeSubDomains

Test Protected Route Headers

curl -I http://localhost:3000/dashboard

# Should include:
# X-Robots-Tag: noindex, nofollow

Testing Authentication

Test Unauthenticated Access

# Try to access protected API without auth
curl http://localhost:3000/api/protected-endpoint

# Expected: 401 Unauthorized
# {
#   "error": "Unauthorized",
#   "message": "Authentication required"
# }

Test Authenticated Access

# With valid Clerk session cookie
curl http://localhost:3000/api/protected-endpoint \
  -H "Cookie: __session=<clerk-session-token>"

# Expected: 200 OK (with authorized response)

Test Authorization (Resource Ownership)

# Try to access another user's resource
curl http://localhost:3000/api/posts/user-abc-post-123 \
  -H "Cookie: __session=<different-user-token>"

# Expected: 403 Forbidden
# {
#   "error": "Forbidden",
#   "message": "You do not have access to this resource"
# }

Test Subscription Gating

# Try premium feature with free account
curl http://localhost:3000/api/premium/generate \
  -H "Cookie: __session=<free-user-token>"

# Expected: 403 Forbidden
# {
#   "error": "Forbidden",
#   "message": "Premium subscription required"
# }

Testing Error Handling

Test Production Error Messages

# Set NODE_ENV=production temporarily
export NODE_ENV=production

# Trigger error in API
curl http://localhost:3000/api/error-test

# Expected: Generic message (no stack trace)
# {
#   "error": "Internal server error",
#   "message": "An unexpected error occurred"
# }

Test Development Error Messages

# In development (NODE_ENV=development)
curl http://localhost:3000/api/error-test

# Expected: Detailed error with stack trace
# {
#   "error": "Internal server error",
#   "message": "Specific error message",
#   "stack": "Error: ...\n    at ...",
#   "context": "error-test"
# }

Testing Dependency Security

Run npm Audit

# Check for vulnerabilities
npm audit

# Expected: 0 vulnerabilities
# found 0 vulnerabilities

Run Production Audit

# Only check production dependencies
npm audit --production

# Expected: 0 vulnerabilities

Check Outdated Packages

npm outdated

# Expected: All packages up-to-date
# (or list of safe minor/patch updates available)

Run Security Check Script

bash scripts/security-check.sh

# Expected:
# - 0 vulnerabilities
# - Minimal outdated packages
# - Fix commands if needed

Online Security Testing Tools

Security Headers Scanner

Tool: https://securityheaders.com/

How to use:

Deploy your app
Enter URL in Security Headers scanner
Check for A+ rating

What it checks:

Content-Security-Policy
X-Frame-Options
X-Content-Type-Options
Strict-Transport-Security
Referrer-Policy
Permissions-Policy

Mozilla Observatory

Tool: https://observatory.mozilla.org/

How to use:

Enter your deployed URL
Run scan
Check score (aim for A+)

What it checks:

Security headers
Cookie security
HTTPS configuration
Subresource integrity
Content Security Policy

SSL Labs

Tool: https://www.ssllabs.com/ssltest/

How to use:

Enter your domain
Wait for scan (takes ~2 minutes)
Check for A+ rating

What it checks:

SSL/TLS configuration
Certificate validity
Protocol support
Cipher suite strength
HSTS configuration

Pre-Deployment Security Checklist

Run through this checklist before every production deployment:

Environment & Configuration

All environment variables set in production
CSRF_SECRET generated and configured (32+ bytes)
SESSION_SECRET generated and configured (32+ bytes)
Clerk production keys configured
Stripe live mode keys configured (if using payments)
.env.local NOT committed to git

Dependencies

Run npm audit --production - 0 vulnerabilities
Run npm outdated - Check for critical updates
package-lock.json committed
Next.js on latest stable version

Security Features

CSRF protection tested (see tests above)
Rate limiting tested (see tests above)
Input validation tested (see tests above)
Security headers verified (securityheaders.com)
HSTS enabled in production
Error messages are generic in production

Authentication & Authorization

Protected routes require authentication
Resource ownership checked before access
Subscription status verified for premium features
Webhook signatures verified (Clerk, Stripe)
Session expiration handled gracefully

API Security

All POST/PUT/DELETE routes have CSRF protection
All public endpoints have rate limiting
All user input validated with Zod
All errors handled with error handler utilities
No sensitive data in logs
No hardcoded secrets in code

Payment Security (if applicable)

Using Clerk Billing + Stripe (not handling cards directly)
Webhooks verified (Svix signatures)
Subscription status checked on server
Test mode disabled in production

Testing

Run rate limit test: node scripts/test-rate-limit.js
Test CSRF protection manually
Test input validation with malicious input
Check security headers: curl -I https://yourapp.com
Test authentication flows
Test error handling in production mode

Monitoring

Error logging configured (Vercel logs)
Failed auth attempts tracked (Clerk dashboard)
GitHub Dependabot alerts enabled
Security headers monitored (automated checks)

Automated Testing Script

security-test.sh

Create a comprehensive test script:

#!/bin/bash

echo "================================="
echo "Security Testing Suite"
echo "================================="
echo ""

# Color codes
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m' # No Color

# Test counter
PASSED=0
FAILED=0

# Function to run test
run_test() {
    local test_name=$1
    local command=$2
    local expected=$3

    echo -n "Testing $test_name... "

    result=$(eval $command 2>&1)

    if echo "$result" | grep -q "$expected"; then
        echo -e "${GREEN}✓ PASS${NC}"
        ((PASSED++))
    else
        echo -e "${RED}✗ FAIL${NC}"
        echo "  Expected: $expected"
        echo "  Got: $result"
        ((FAILED++))
    fi
}

echo "=== Dependency Security ==="
run_test "npm audit" "npm audit --production" "found 0 vulnerabilities"

echo ""
echo "=== Rate Limiting ==="
echo "Running rate limit test script..."
node scripts/test-rate-limit.js

echo ""
echo "=== Security Headers ==="
run_test "X-Frame-Options" "curl -I http://localhost:3000" "X-Frame-Options: DENY"
run_test "X-Content-Type-Options" "curl -I http://localhost:3000" "X-Content-Type-Options: nosniff"
run_test "Content-Security-Policy" "curl -I http://localhost:3000" "Content-Security-Policy"

echo ""
echo "================================="
echo "Tests Passed: $PASSED"
echo "Tests Failed: $FAILED"
echo "================================="

if [ $FAILED -eq 0 ]; then
    echo -e "${GREEN}All tests passed!${NC}"
    exit 0
else
    echo -e "${RED}Some tests failed!${NC}"
    exit 1
fi

Run it:

bash scripts/security-test.sh

Continuous Security Testing

Add to CI/CD Pipeline

# .github/workflows/security.yml
name: Security Tests

on:
  push:
    branches: [ main ]
  pull_request:
    branches: [ main ]

jobs:
  security:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '18'

      - name: Install dependencies
        run: npm ci

      - name: Run npm audit
        run: npm audit --production

      - name: Check for outdated packages
        run: npm outdated || true

      - name: Build application
        run: npm run build

      - name: Start server (background)
        run: npm run dev &
        env:
          NODE_ENV: test

      - name: Wait for server
        run: npx wait-on http://localhost:3000

      - name: Run security tests
        run: bash scripts/security-test.sh

      - name: Stop server
        run: pkill -f "npm run dev"

Manual Penetration Testing

Test XSS in All Input Fields

Try these payloads in every input:

<script>alert('XSS')</script>
<img src=x onerror=alert('XSS')>
<svg onload=alert('XSS')>
javascript:alert('XSS')
"><script>alert('XSS')</script>

Verify all are sanitized

Test SQL Injection

Try these in search/query fields:

' OR '1'='1
'; DROP TABLE users; --
' UNION SELECT * FROM users --

Verify input validation blocks or sanitizes

Test CSRF

Create malicious HTML file:

<form action="http://localhost:3000/api/delete-account" method="POST">
  <input type="hidden" name="confirm" value="yes" />
</form>
<script>document.forms[0].submit();</script>

Open while logged in
Verify request blocked (403 Forbidden)

Test Authorization

Create resource as User A
Try to access/modify as User B
Verify 403 Forbidden

What To Monitor Post-Deployment

Daily

Error rates (Vercel dashboard)
Failed authentication attempts (Clerk dashboard)
Rate limit violations (check logs for 429 responses)

Weekly

Run npm audit --production
Check GitHub Dependabot alerts
Review error logs for patterns

Monthly

Full security audit
Update dependencies
Re-run security testing suite
Check security headers (securityheaders.com)

References

OWASP Testing Guide: https://owasp.org/www-project-web-security-testing-guide/
Security Headers Scanner: https://securityheaders.com/
Mozilla Observatory: https://observatory.mozilla.org/
SSL Labs: https://www.ssllabs.com/ssltest/
npm Audit: https://docs.npmjs.com/cli/v8/commands/npm-audit

Next Steps

For fixing issues: Use appropriate security skill (csrf-protection, rate-limiting, etc.)
For deployment: Complete pre-deployment checklist above
For monitoring: Set up automated security scans in CI/CD
For ongoing maintenance: Run monthly security audit

security-testing-verification

Security Testing & Verification

Built-In Security Tests

Testing Rate Limiting

Automated Test Script