Security Testing Checklist for Web Applications

Security vulnerabilities in web applications can devastate businesses. Data breaches, ransomware, and regulatory fines are just the beginning. Prevention starts with thorough security testing.

This guide walks you through essential security tests every web application needs, explaining not just what to test, but why each area matters for protecting your users and business.

Top Security Vulnerabilities to Test For

Understanding which vulnerabilities pose the greatest risk helps prioritize your security testing efforts. The top threats include injection attacks like SQL injection and XSS that exploit insufficient input validation, broken authentication mechanisms that allow account takeover, insecure authorization enabling unauthorized data access, sensitive data exposure through inadequate encryption, and misconfigured security settings that create exploitable gaps. These OWASP Top 10 vulnerabilities account for the majority of successful attacks and should be your primary focus in security testing.

Authentication Testing

Authentication is your application's first line of defense. When authentication fails, everything downstream becomes vulnerable. Strong password policies and session management aren't just recommendations - they're necessities in a world where credential-based attacks remain the most common entry point for breaches.

Password Security

Modern password security goes beyond simple length requirements. Your application should enforce a minimum of 12 characters with mixed case, numbers, and symbols - but that's just the start. You need to actively reject common passwords like "password123" or "qwerty" that attackers try first. More critically, passwords must be stored using modern hashing algorithms like bcrypt or Argon2. If you're still using MD5 or SHA1, you're essentially storing passwords in plain text from a security perspective.

One often-overlooked detail: your password reset flow shouldn't reveal whether an email address exists in your system. This small information leak can help attackers enumerate valid user accounts.

Session Management

Session security determines whether an attacker can hijack a user's authenticated session. Your session tokens must be cryptographically random - predictable tokens are as bad as weak passwords. Sessions should expire after inactivity (typically 15-30 minutes for sensitive applications), and logout must truly invalidate the session server-side, not just clear a client-side cookie.

Never expose session tokens in URLs where they can leak through browser history, proxy logs, or referrer headers. Set the Secure and HttpOnly flags on session cookies to prevent transmission over unencrypted connections and protect against XSS attacks.

Multi-Factor Authentication

For sensitive operations - financial transactions, personal data access, administrative actions - single-factor authentication isn't sufficient. MFA provides a critical safety net when passwords are compromised. Always provide backup codes for account recovery, and ensure there's no way to bypass MFA through social engineering of your support channels. Attackers know that help desks are often the weakest link.

Authorization Testing

Authentication confirms who users are. Authorization confirms what they can do. Getting authorization wrong means users can access data they shouldn't see or perform actions they shouldn't execute. These vulnerabilities are harder to detect through automated scanning and require thoughtful manual testing.

Access Control

Every data access request needs authorization validation. Users should only see their own data, and this rule must be enforced server-side where attackers can't bypass it. Role-based permissions provide structure, but they're only effective if checked on every API endpoint - not just the UI.

Test for privilege escalation by attempting to access administrative functions from regular user accounts. Try manipulating direct object references (like changing a user ID in a URL from 123 to 124) to access other users' data. These attacks are surprisingly common because developers sometimes assume users will only request their own data through the UI.

Admin Functions

Administrative functionality deserves extra scrutiny. Admin panels should require additional authentication, not just a different role flag. All admin actions should be logged for audit purposes - you need to know who did what and when if something goes wrong. Consider implementing separate, stronger policies for admin accounts, including mandatory MFA and more aggressive session timeouts.

Input Validation Testing

Most security vulnerabilities stem from insufficient input validation. Attackers inject malicious code through input fields, and if your application trusts that input, you're vulnerable. Input validation testing protects against injection attacks that can compromise your database, execute arbitrary code, or steal user data.

Injection Prevention

SQL injection remains one of the most dangerous vulnerabilities. Test by entering queries like \