# Security Checklist

> **Tooling note:** Commands using `./node_modules/.bin/` assume the tool is already declared at a reviewed/pinned version and installed from the project lockfile. If it is missing, ask before adding a dependency; do not fall back to `npx` auto-install.


Quick reference for web application security. Use alongside the `security-and-hardening` skill.

## Table of Contents

- [Threat Modeling (Start Here)](#threat-modeling-start-here)
- [Pre-Commit Checks](#pre-commit-checks)
- [Authentication](#authentication)
- [Authorization](#authorization)
- [Input Validation](#input-validation)
- [Security Headers](#security-headers)
- [CORS Configuration](#cors-configuration)
- [Data Protection](#data-protection)
- [Dependency Security](#dependency-security)
- [AI / LLM Security](#ai--llm-security)
- [Error Handling](#error-handling)
- [OWASP Top 10 Quick Reference](#owasp-top-10-quick-reference)
- [OWASP Top 10 for LLMs Quick Reference](#owasp-top-10-for-llms-quick-reference)

## Threat Modeling (Start Here)

Before reaching for controls, spend five minutes thinking like an attacker:

- [ ] Trust boundaries mapped (requests, uploads, webhooks, third-party APIs, LLM output)
- [ ] Assets named (credentials, PII, payment data, admin actions, money movement)
- [ ] STRIDE run per boundary (Spoofing, Tampering, Repudiation, Info disclosure, DoS, Elevation)
- [ ] Abuse cases written next to use cases ("how would I misuse this?")

## Pre-Commit Checks

- [ ] No secrets in code (`git diff --cached | grep -i "password\|secret\|api_key\|token"`)
- [ ] `.gitignore` covers: `.env`, `.env.local`, `*.pem`, `*.key`
- [ ] `.env.example` uses placeholder values (not real secrets)

## Authentication

- [ ] Passwords hashed with bcrypt (≥12 rounds), scrypt, or argon2
- [ ] Session cookies: `httpOnly`, `secure`, `sameSite: 'lax'`
- [ ] Session expiration configured (reasonable max-age)
- [ ] Rate limiting on login endpoint (≤10 attempts per 15 minutes)
- [ ] Password reset tokens: time-limited (≤1 hour), single-use
- [ ] Account lockout after repeated failures (optional, with notification)
- [ ] MFA supported for sensitive operations (optional but recommended)

## Authorization

- [ ] Every protected endpoint checks authentication
- [ ] Every resource access checks ownership/role (prevents IDOR)
- [ ] Admin endpoints require admin role verification
- [ ] API keys scoped to minimum necessary permissions
- [ ] JWT tokens validated (signature, expiration, issuer)

## Input Validation

- [ ] All user input validated at system boundaries (API routes, form handlers)
- [ ] Validation uses allowlists (not denylists)
- [ ] String lengths constrained (min/max)
- [ ] Numeric ranges validated
- [ ] Email, URL, and date formats validated with proper libraries
- [ ] File uploads: type restricted, size limited, content verified
- [ ] SQL queries parameterized (no string concatenation)
- [ ] HTML output encoded (use framework auto-escaping)
- [ ] URLs validated before redirect (prevent open redirect)
- [ ] Server-side URL fetches allowlisted; private/reserved IPs blocked (prevent SSRF)

## Security Headers

```
Content-Security-Policy: default-src 'self'; script-src 'self'
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 0  (disabled, rely on CSP)
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()
```

## CORS Configuration

```typescript
// Restrictive (recommended)
cors({
  origin: ['https://yourdomain.com', 'https://app.yourdomain.com'],
  credentials: true,
  methods: ['GET', 'POST', 'PUT', 'PATCH', 'DELETE'],
  allowedHeaders: ['Content-Type', 'Authorization'],
})

// NEVER use in production:
cors({ origin: '*' })  // Allows any origin
```

## Data Protection

- [ ] Sensitive fields excluded from API responses (`passwordHash`, `resetToken`, etc.)
- [ ] Sensitive data not logged (passwords, tokens, full CC numbers)
- [ ] PII encrypted at rest (if required by regulation)
- [ ] HTTPS for all external communication
- [ ] Database backups encrypted

## Dependency Security

```bash
# Audit dependencies
npm audit

# Fix automatically where possible
npm audit fix

# Check for critical vulnerabilities
npm audit --audit-level=critical

# Keep dependencies updated
./node_modules/.bin/npm-check-updates
```

**Supply-chain hygiene** (`npm audit` won't catch malicious packages):
- [ ] Lockfile committed; CI installs with `npm ci` (not `npm install`)
- [ ] New dependencies reviewed (maintenance, downloads, `postinstall` scripts)
- [ ] No typosquats (`cross-env` vs `crossenv`, `react-dom` vs `reactdom`)

## AI / LLM Security

For any feature that calls an LLM (chatbots, summarizers, agents, RAG):

- [ ] Model output treated as untrusted — never into `eval`/SQL/shell/`innerHTML`/file paths
- [ ] Prompt injection assumed; permissions enforced in code, not in the system prompt
- [ ] Secrets, cross-tenant data, and full system prompts kept out of the context window
- [ ] Tool/agent permissions scoped; destructive or irreversible actions require confirmation
- [ ] Token, rate, and recursion/loop limits set (bound consumption)

## Error Handling

```typescript
// Production: generic error, no internals
res.status(500).json({
  error: { code: 'INTERNAL_ERROR', message: 'Something went wrong' }
});

// NEVER in production:
res.status(500).json({
  error: err.message,
  stack: err.stack,         // Exposes internals
  query: err.sql,           // Exposes database details
});
```

## OWASP Top 10 Quick Reference

| # | Vulnerability | Prevention |
|---|---|---|
| 1 | Broken Access Control | Auth checks on every endpoint, ownership verification |
| 2 | Cryptographic Failures | HTTPS, strong hashing, no secrets in code |
| 3 | Injection | Parameterized queries, input validation |
| 4 | Insecure Design | Threat modeling, spec-driven development |
| 5 | Security Misconfiguration | Security headers, minimal permissions, audit deps |
| 6 | Vulnerable Components | `npm audit`, keep deps updated, minimal deps |
| 7 | Auth Failures | Strong passwords, rate limiting, session management |
| 8 | Data Integrity Failures | Verify updates/dependencies, signed artifacts |
| 9 | Logging Failures | Log security events, don't log secrets |
| 10 | SSRF | Validate/allowlist URLs, restrict outbound requests |

## OWASP Top 10 for LLMs Quick Reference

For apps with LLM features. See the [OWASP GenAI Security Project](https://genai.owasp.org/llm-top-10/).

| ID | Risk | Prevention |
|---|---|---|
| LLM01 | Prompt Injection | Don't trust the system prompt as a boundary; enforce permissions in code |
| LLM02 | Sensitive Information Disclosure | Keep secrets/PII out of prompts; filter outputs |
| LLM03 | Supply Chain | Vet models, datasets, and plugins like any dependency |
| LLM04 | Data and Model Poisoning | Use trusted model sources, verify integrity; vet fine-tuning and RAG data |
| LLM05 | Improper Output Handling | Treat model output as untrusted; validate, parameterize, encode |
| LLM06 | Excessive Agency | Scope tool permissions; confirm destructive actions |
| LLM07 | System Prompt Leakage | Assume the system prompt can leak; put no secrets in it |
| LLM08 | Vector and Embedding Weaknesses | Partition RAG embeddings per tenant; validate documents before indexing |
| LLM09 | Misinformation | Ground answers with citations; validate critical claims; keep a human in the loop |
| LLM10 | Unbounded Consumption | Cap tokens, request rate, and loop/recursion depth |