Injection Attacks

Injection attacks are a common and dangerous type of security vulnerability in web applications and APIs. They occur when an attacker sends malicious data as part of an input, tricking the application into executing unintended commands or accessing unauthorized data.

These attacks matter because they can lead to serious consequences, including:

• Unauthorized access to sensitive information;
• Data corruption or loss;
• Full system compromise by executing arbitrary commands.

Understanding injection attacks is essential for anyone working in cybersecurity. Recognizing how these attacks work helps you identify, prevent, and mitigate them, keeping your applications and data secure from potential threats.

Common Types of Injection Vulnerabilities

Injection vulnerabilities let attackers send malicious data to an application, tricking it into performing unintended actions. Here are some of the most common types you need to recognize:

SQL Injection

SQL Injection happens when user input is sent directly into a SQL query without proper validation or sanitization. Attackers can use this to access, modify, or delete data in your database.

Example:

Suppose a login form uses this code:

SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "';

If you enter admin' -- as the username and anything as the password, the query becomes:

SELECT * FROM users WHERE username = 'admin' --' AND password = '';

The -- turns the rest of the line into a comment, so the password check is skipped. You are logged in as admin without knowing the password.

Command Injection

Command Injection allows attackers to run system commands on the server by injecting malicious input into functions that build shell commands.

Example:

A web form lets users check if a server is online by entering an IP address. The server runs this code:

ping " + ip_address + "

If you enter 8.8.8.8; cat /etc/passwd, the server runs:

ping 8.8.8.8; cat /etc/passwd

This command not only pings the address but also shows sensitive user information from the /etc/passwd file.

Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) lets attackers inject malicious scripts into web pages viewed by other users. These scripts can steal cookies, hijack sessions, or manipulate web content.

Example:

A comments section displays user input without filtering. If you post this comment:

<script>alert('Hacked!');</script>

Everyone who views the page will see a popup with the message Hacked!. Attackers can use similar scripts for more harmful actions, such as stealing session tokens.

Understanding these vulnerabilities helps you recognize risky patterns and protect your applications from common attacks.