Security Review Skill

This skill ensures all code follows security best practices and identifies potential vulnerabilities.

When to Activate

• Implementing authentication or authorization

• Handling user input or file uploads

• Creating new API endpoints

• Working with secrets or credentials

• Implementing payment features

• Storing or transmitting sensitive data

• Integrating third-party APIs

Security Checklist

1. Secrets Management

❌ NEVER Do This

const apiKey = "sk-proj-xxxxx" // Hardcoded secret const dbPassword = "password123" // In source code

✅ ALWAYS Do This

const apiKey = process.env.OPENAI_API_KEY const dbUrl = process.env.DATABASE_URL

// Verify secrets exist if (!apiKey) { throw new Error('OPENAI_API_KEY not configured') }

Verification Steps

• No hardcoded API keys, tokens, or passwords

• All secrets in environment variables

• .env.local in .gitignore

• No secrets in git history

• Production secrets in hosting platform (Vercel, Railway)

2. Input Validation

Always Validate User Input

import { z } from 'zod'

// Define validation schema const CreateUserSchema = z.object({ email: z.string().email(), name: z.string().min(1).max(100), age: z.number().int().min(0).max(150) })

// Validate before processing export async function createUser(input: unknown) { try { const validated = CreateUserSchema.parse(input) return await db.users.create(validated) } catch (error) { if (error instanceof z.ZodError) { return { success: false, errors: error.errors } } throw error } }

File Upload Validation

function validateFileUpload(file: File) { // Size check (5MB max) const maxSize = 5 * 1024 * 1024 if (file.size > maxSize) { throw new Error('File too large (max 5MB)') }

// Type check const allowedTypes = ['image/jpeg', 'image/png', 'image/gif'] if (!allowedTypes.includes(file.type)) { throw new Error('Invalid file type') }

// Extension check const allowedExtensions = ['.jpg', '.jpeg', '.png', '.gif'] const extension = file.name.toLowerCase().match(/.[^.]+$/)?.[0] if (!extension || !allowedExtensions.includes(extension)) { throw new Error('Invalid file extension') }

return true }

Verification Steps

• All user inputs validated with schemas

• File uploads restricted (size, type, extension)

• No direct use of user input in queries

• Whitelist validation (not blacklist)

• Error messages don't leak sensitive info

3. SQL Injection Prevention

❌ NEVER Concatenate SQL

// DANGEROUS - SQL Injection vulnerability const query = SELECT * FROM users WHERE email = '${userEmail}' await db.query(query)

✅ ALWAYS Use Parameterized Queries

// Safe - parameterized query const { data } = await supabase .from('users') .select('*') .eq('email', userEmail)

// Or with raw SQL await db.query( 'SELECT * FROM users WHERE email = $1', [userEmail] )

Verification Steps

• All database queries use parameterized queries

• No string concatenation in SQL

• ORM/query builder used correctly

• Supabase queries properly sanitized

4. Authentication & Authorization

JWT Token Handling

// ❌ WRONG: localStorage (vulnerable to XSS) localStorage.setItem('token', token)

// ✅ CORRECT: httpOnly cookies res.setHeader('Set-Cookie', token=${token}; HttpOnly; Secure; SameSite=Strict; Max-Age=3600)

Authorization Checks

export async function deleteUser(userId: string, requesterId: string) { // ALWAYS verify authorization first const requester = await db.users.findUnique({ where: { id: requesterId } })

if (requester.role !== 'admin') { return NextResponse.json( { error: 'Unauthorized' }, { status: 403 } ) }

// Proceed with deletion await db.users.delete({ where: { id: userId } }) }

Row Level Security (Supabase)

-- Enable RLS on all tables ALTER TABLE users ENABLE ROW LEVEL SECURITY;

-- Users can only view their own data CREATE POLICY "Users view own data" ON users FOR SELECT USING (auth.uid() = id);

-- Users can only update their own data CREATE POLICY "Users update own data" ON users FOR UPDATE USING (auth.uid() = id);

Verification Steps

• Tokens stored in httpOnly cookies (not localStorage)

• Authorization checks before sensitive operations

• Row Level Security enabled in Supabase

• Role-based access control implemented

• Session management secure

5. XSS Prevention

Sanitize HTML

import DOMPurify from 'isomorphic-dompurify'

// ALWAYS sanitize user-provided HTML function renderUserContent(html: string) { const clean = DOMPurify.sanitize(html, { ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'p'], ALLOWED_ATTR: [] }) return <div dangerouslySetInnerHTML={{ __html: clean }} /> }

Content Security Policy

// next.config.js const securityHeaders = [ { key: 'Content-Security-Policy', value: default-src 'self'; script-src 'self' 'unsafe-eval' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self'; connect-src 'self' https://api.example.com; .replace(/\s{2,}/g, ' ').trim() } ]

Verification Steps

• User-provided HTML sanitized

• CSP headers configured

• No unvalidated dynamic content rendering

• React's built-in XSS protection used

6. CSRF Protection

CSRF Tokens

import { csrf } from '@/lib/csrf'

export async function POST(request: Request) { const token = request.headers.get('X-CSRF-Token')

if (!csrf.verify(token)) { return NextResponse.json( { error: 'Invalid CSRF token' }, { status: 403 } ) }

// Process request }

SameSite Cookies

res.setHeader('Set-Cookie', session=${sessionId}; HttpOnly; Secure; SameSite=Strict)

Verification Steps

• CSRF tokens on state-changing operations

• SameSite=Strict on all cookies

• Double-submit cookie pattern implemented

7. Rate Limiting

API Rate Limiting

import rateLimit from 'express-rate-limit'

const limiter = rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 100, // 100 requests per window message: 'Too many requests' })

// Apply to routes app.use('/api/', limiter)

Expensive Operations

// Aggressive rate limiting for searches const searchLimiter = rateLimit({ windowMs: 60 * 1000, // 1 minute max: 10, // 10 requests per minute message: 'Too many search requests' })

app.use('/api/search', searchLimiter)

Verification Steps

• Rate limiting on all API endpoints

• Stricter limits on expensive operations

• IP-based rate limiting

• User-based rate limiting (authenticated)

8. Sensitive Data Exposure

Logging

// ❌ WRONG: Logging sensitive data console.log('User login:', { email, password }) console.log('Payment:', { cardNumber, cvv })

// ✅ CORRECT: Redact sensitive data console.log('User login:', { email, userId }) console.log('Payment:', { last4: card.last4, userId })

Error Messages

// ❌ WRONG: Exposing internal details catch (error) { return NextResponse.json( { error: error.message, stack: error.stack }, { status: 500 } ) }

// ✅ CORRECT: Generic error messages catch (error) { console.error('Internal error:', error) return NextResponse.json( { error: 'An error occurred. Please try again.' }, { status: 500 } ) }

Verification Steps

• No passwords, tokens, or secrets in logs

• Error messages generic for users

• Detailed errors only in server logs

• No stack traces exposed to users

9. Blockchain Security (Solana)

Wallet Verification

import { verify } from '@solana/web3.js'

async function verifyWalletOwnership( publicKey: string, signature: string, message: string ) { try { const isValid = verify( Buffer.from(message), Buffer.from(signature, 'base64'), Buffer.from(publicKey, 'base64') ) return isValid } catch (error) { return false } }

Transaction Verification

async function verifyTransaction(transaction: Transaction) { // Verify recipient if (transaction.to !== expectedRecipient) { throw new Error('Invalid recipient') }

// Verify amount if (transaction.amount > maxAmount) { throw new Error('Amount exceeds limit') }

// Verify user has sufficient balance const balance = await getBalance(transaction.from) if (balance < transaction.amount) { throw new Error('Insufficient balance') }

return true }

Verification Steps

• Wallet signatures verified

• Transaction details validated

• Balance checks before transactions

• No blind transaction signing

10. Dependency Security

Regular Updates

Check for vulnerabilities

npm audit

Fix automatically fixable issues

npm audit fix

Update dependencies

npm update

Check for outdated packages

npm outdated

Lock Files

ALWAYS commit lock files

git add package-lock.json

Use in CI/CD for reproducible builds

npm ci # Instead of npm install

Verification Steps

• Dependencies up to date

• No known vulnerabilities (npm audit clean)

• Lock files committed

• Dependabot enabled on GitHub

• Regular security updates

Security Testing

Automated Security Tests

// Test authentication test('requires authentication', async () => { const response = await fetch('/api/protected') expect(response.status).toBe(401) })

// Test authorization test('requires admin role', async () => { const response = await fetch('/api/admin', { headers: { Authorization: Bearer ${userToken} } }) expect(response.status).toBe(403) })

// Test input validation test('rejects invalid input', async () => { const response = await fetch('/api/users', { method: 'POST', body: JSON.stringify({ email: 'not-an-email' }) }) expect(response.status).toBe(400) })

// Test rate limiting test('enforces rate limits', async () => { const requests = Array(101).fill(null).map(() => fetch('/api/endpoint') )

const responses = await Promise.all(requests) const tooManyRequests = responses.filter(r => r.status === 429)

expect(tooManyRequests.length).toBeGreaterThan(0) })

Pre-Deployment Security Checklist

Before ANY production deployment:

• Secrets: No hardcoded secrets, all in env vars

• Input Validation: All user inputs validated

• SQL Injection: All queries parameterized

• XSS: User content sanitized

• CSRF: Protection enabled

• Authentication: Proper token handling

• Authorization: Role checks in place

• Rate Limiting: Enabled on all endpoints

• HTTPS: Enforced in production

• Security Headers: CSP, X-Frame-Options configured

• Error Handling: No sensitive data in errors

• Logging: No sensitive data logged

• Dependencies: Up to date, no vulnerabilities

• Row Level Security: Enabled in Supabase

• CORS: Properly configured

• File Uploads: Validated (size, type)

• Wallet Signatures: Verified (if blockchain)

Resources

• OWASP Top 10

• Next.js Security

• Supabase Security

• Web Security Academy

Remember: Security is not optional. One vulnerability can compromise the entire platform. When in doubt, err on the side of caution.