The 100 Web Vulnerabilities Every Cybersecurity Pro Must Master: Your Ultimate Cheat Sheet

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Introduction:

Web application security is the frontline of modern digital defense, encompassing everything from critical infrastructure to personal data. Understanding the vast landscape of potential vulnerabilities is the first step toward building impregnable systems and becoming an effective ethical hacker. This guide distills the most critical web threats into actionable knowledge for penetration testers, developers, and security architects.

Learning Objectives:

  • Identify and differentiate between the top 100 web application vulnerability classes.
  • Execute basic exploitation techniques for critical vulnerabilities to understand their impact.
  • Implement verified mitigation strategies and commands to harden systems against these attacks.

You Should Know:

1. SQL Injection (SQLi) Exploitation and Mitigation

`sqlmap -u “http://example.com/page?id=1” –batch –dbs`
This command launches the sqlmap tool to automatically test the URL parameter `id` for SQL injection vulnerabilities. The `–batch` flag runs it in non-interactive mode, accepting default options, and `–dbs` attempts to enumerate available databases upon successful injection.

Step-by-Step Guide:

  1. Identify a Target: Find a webpage that uses a query parameter, like example.com/page?id=1.
  2. Test Manually: Append a single quote (') to the parameter (id=1'). If the page returns a database error, it is likely vulnerable.
  3. Automate with sqlmap: Use the command above, replacing the URL with your target.
  4. Mitigation: The primary defense is using Prepared Statements (Parameterized Queries) in code. For example, in Java:
    `String query = “SELECT FROM users WHERE id = ?”;`

`PreparedStatement stmt = connection.prepareStatement(query);`

`stmt.setString(1, userId);`

2. Cross-Site Scripting (XSS) Payload Delivery

``
This is a basic reflected XSS payload. When injected into a vulnerable web page, it forces a victim’s browser to send their session cookie to a server controlled by an attacker.

Step-by-Step Guide:

  1. Find an Input Field: Locate a search box, comment form, or URL parameter that reflects input back to the page.
  2. Test for Validation: Input a simple script tag (<script>alert('XSS')</script>). If an alert box pops up, it’s vulnerable.
  3. Deliver a Malicious Payload: Replace the proof-of-concept alert with the exfiltration payload shown above.
  4. Mitigation: Implement robust output encoding. Context is key: use HTML entity encoding for HTML content (&lt; for <) and JavaScript encoding for content within `