Injection attacks are among the most dangerous security vulnerabilities in web applications. By manipulating user input, attackers can execute malicious database queries, gain unauthorized access, or inject harmful scripts into web pages. These attacks compromise data integrity, expose sensitive information, and can even lead to a full system takeover.

Let’s examine three common injection attacks—SQL injection, NoSQL injection, and cross-site scripting (XSS)—and how to defend against them in Express.

Understanding injection attacks

Injection attacks occur when an application fails to properly validate or sanitize user input. This allows attackers to modify queries, execute code, or inject scripts, potentially gaining unauthorized access or exposing sensitive data.

The three major types of injection attacks are:

  • SQL injection: It exploits vulnerabilities in SQL queries to manipulate databases.

  • NoSQL injection: It targets NoSQL databases like MongoDB by injecting malicious objects into queries.

  • Cross-site scripting (XSS): It injects malicious scripts into web pages, affecting users who view them.

Understanding these attacks helps us build more secure applications. Let’s examine them one by one.

Preventing SQL injection

SQL injection happens when an application constructs an SQL query by directly embedding user input without proper validation or sanitization. This allows attackers to manipulate queries and access unauthorized data.

How SQL injection works

Consider this vulnerable Express.js route:

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