보안

# Bad - vulnerable to injection
query = f"from:{user_input}"

# Good - validate input first
import re
if re.match(r'^[a-zA-Z0-9_]{1,15}$', user_input):
    query = f"from:{user_input}"

// Bad - vulnerable to XSS
element.innerHTML = tweet.text;

// Good - escape HTML
element.textContent = tweet.text;

import secrets

# Generate state before authorization
state = secrets.token_urlsafe(32)
session['oauth_state'] = state

# Verify state after callback
if request.args.get('state') != session.get('oauth_state'):
    abort(403)  # State mismatch - possible CSRF