Injection attacks are a type of security threat where an attacker sends malicious data into an application to make it behave in unintended ways. This happens when user input is not properly checked or filtered before being used by the application. Attackers can use this weakness to access sensitive information, change data, or even take control of the entire system.

Injection attacks are dangerous because:

• They can allow attackers to steal usernames, passwords, or other confidential data;
• They may let attackers modify or delete important information;
• They can give attackers control over your application or server;
• They often bypass normal security measures, making them difficult to detect.

Understanding injection attacks is critical for anyone building or managing applications, as these vulnerabilities are common and can cause severe damage if left unaddressed.

Common Types of Injection Attacks

Injection attacks occur when untrusted data is sent to an interpreter as part of a command or query. Attackers use these vulnerabilities to execute malicious commands or access unauthorized data. The most common types of injection attacks include:

• SQL injection: attackers insert malicious SQL statements into input fields to manipulate a database. This can allow unauthorized access, data theft, or data modification;
• Command injection: attackers supply operating system commands through a vulnerable application, causing the system to execute unintended commands. This can result in file manipulation, data exfiltration, or privilege escalation;
• LDAP injection: attackers modify LDAP queries with user-supplied data, potentially bypassing authentication or accessing unauthorized information;
• XML injection: attackers insert malicious XML content into a message or query, which can disrupt application logic or expose sensitive data;
• Code injection: attackers inject code into an application, causing it to run arbitrary scripts or programs. This can compromise the application's integrity and security.

You will learn how these attacks work and how to defend against them in the following sections.

How Attackers Exploit Unvalidated Input

Attackers target applications that do not properly validate or sanitize user input. When you accept input from users—such as form fields, URL parameters, or cookies—without checking its content, you create opportunities for attackers to manipulate how your application works.

Manipulating Application Behavior

Attackers can send specially crafted data that changes the logic of your application. For example:

• Submitting unexpected characters or code in a login form to bypass authentication;
• Altering query parameters in a URL to access features or data not intended for them;
• Injecting commands or scripts that your application executes, leading to unintended actions.

Accessing Sensitive Data

If you use user input in database queries, file paths, or system commands without validation, attackers can:

• Retrieve confidential information from your database by adding SQL code to input fields;
• Read or modify files on your server by changing the value of file path parameters;
• Gain access to user accounts or internal resources by manipulating session data or authentication tokens.

Always validate and sanitize all user input to prevent attackers from exploiting these vulnerabilities and to keep your application secure.