Security Backend Checklist

When to Use

When implementing backend APIs, database queries, authentication, or handling user input.

Patterns

Input Validation

// ✅ Whitelist validation with Zod
const userSchema = z.object({
  email: z.string().email().max(255),
  age: z.number().int().min(0).max(150),
});
const validated = userSchema.parse(userInput);

SQL Injection Prevention

// ❌ NEVER - string concatenation
const query = `SELECT * FROM users WHERE id = ${userId}`;

// ✅ ALWAYS - parameterized queries
const query = 'SELECT * FROM users WHERE id = $1';
await db.query(query, [userId]);

Secrets Management

// ❌ NEVER
const apiKey = 'sk-1234567890abcdef';

// ✅ ALWAYS
const apiKey = process.env.API_KEY;
// + .env in .gitignore

Error Handling

// ❌ Exposes internals
catch (error) {
  return res.status(500).json({ error: error.stack, query: sql });
}

// ✅ Safe response
catch (error) {
  logger.error('DB error', { error, userId });
  return res.status(500).json({ error: 'Internal server error' });
}

Access Control (Top OWASP Risk)

// ✅ Check auth on EVERY endpoint
async function getResource(userId: string, resourceId: string) {
  const resource = await db.resource.findUnique({ where: { id: resourceId } });
  if (!resource || resource.ownerId !== userId) {
    throw new ForbiddenError('Access denied');
  }
  return resource;
}

Anti-Patterns

• Trusting client-side validation alone
• Storing passwords in plaintext (use bcrypt/argon2)
• Hardcoded secrets in code
• Exposing stack traces in production
• Missing rate limiting on auth endpoints
• Not validating third-party dependencies (supply chain risk)

Verification Checklist

• All user input validated server-side
• Parameterized queries everywhere (no string concat)
• No secrets in code (all from env vars)
• Passwords hashed (bcrypt/argon2)
• Auth checked on EVERY endpoint
• Rate limiting on login/register
• Error responses don't leak internals
• HTTPS enforced
• Security misconfiguration checks (headers, CORS)
• Dependencies audited (npm audit, supply chain)

Context

Based on OWASP Top Ten 2021 (latest released standard). Note: 2025 RC emphasizes supply chain security and access control as top priorities.