When it comes to web application vulnerabilities, SQL Injection (SQLi) is one of the oldest yet most dangerous threats developers must guard against. Despite being well-known, it continues to make its way into real-world systems, causing data leaks, financial loss, and reputational damage.

Let’s break it down.

What is SQL Injection?

SQL Injection is a type of attack where malicious users “inject” crafted SQL queries into an application’s database layer.
This usually happens when user input is not properly validated or sanitised before being used in a database query.

For example:

// Insecure login query
const query = `SELECT * FROM users WHERE username = '${username}' AND password = '${password}'`;

If a user enters the following as their username:

' OR '1'='1

The resulting query becomes:

SELECT * FROM users WHERE username = '' OR '1'='1' AND password = '...';


This condition always evaluates to true, allowing attackers to log in without valid credentials.

Why is SQL Injection Dangerous?

SQL Injection gives attackers direct access to your database. Depending on permissions, they can:

• Steal sensitive data (usernames, emails, passwords).
• Delete or modify records.
• Execute administrative operations.
• In extreme cases, gain full control of the database server.

According to the OWASP Top 10, Injection attacks remain among the most critical security risks in modern applications.

Real-World Impact

• 2008 Heartland Payment Systems breach – attackers used SQLi to steal millions of credit card records.
• 2012 Yahoo! breach – SQLi exposed over 450,000 usernames and passwords.

These examples prove that ignoring SQLi can lead to catastrophic consequences.

How to Prevent SQL Injection

1. Use Prepared Statements (Parameterised Queries)
   Instead of embedding variables directly into queries, bind them as parameters: Here, the database treats username and password as data, not executable SQL.

// Safe query using parameterisation
const query = "SELECT * FROM users WHERE username = ? AND password = ?";
db.execute(query, [username, password]);

1. Use ORM or Query Builders
   Frameworks like Prisma, Sequelize, or TypeORM abstract raw SQL, making injection harder.
2. Validate and Sanitize Input
   Always enforce strict rules for input formats (e.g., email regex, numeric IDs).
3. Principle of Least Privilege
   Ensure your database user has only the permissions it needs.
4. Regular Security Testing
   Use tools for static analysis and penetration testing to catch vulnerabilities early.

SQL Injection in Modern Development

While frameworks (like Next.js, Django, Spring) reduce the chances of SQLi through abstractions, developers still need to understand the risk. One insecure raw query is enough to expose an entire system.

Final Thoughts

SQL Injection is like leaving the backdoor of your application wide open. As developers, our job isn’t just writing working code bit’s writing secure code.

The first defense is awareness. Once you understand how SQLi works, preventing it becomes straightforward:

• Use prepared statements.
• Validate input.
• Limit privileges.

By adopting these practices, you protect both your users and your application from one of the most devastating vulnerabilities in web security.