Introduction to Web Application Security

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Introduction to Web Application Security

Web application security is a critical aspect of modern software development. This post covers the fundamentals of identifying and mitigating common vulnerabilities.

Common Vulnerabilities

SQL Injection

SQL Injection occurs when untrusted data is sent to an interpreter as part of a command or query. This can lead to unauthorized access to data.

-- Vulnerable query
SELECT * FROM users WHERE username = '$username' AND password = '$password'

-- Exploited
username: admin' OR '1'='1

Cross-Site Scripting (XSS)

XSS vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.

// Vulnerable code
document.getElementById('output').innerHTML = userInput;

// Safe alternative
document.getElementById('output').textContent = userInput;

Best Practices

  1. Always validate and sanitize user input
  2. Use parameterized queries for database operations
  3. Implement Content Security Policy (CSP)
  4. Keep dependencies up to date
  5. Regular security audits and penetration testing