SQL Injection

SQL Injection is one of the most widespread and dangerous vulnerabilities in web applications. It occurs when user-supplied input is inserted directly into SQL queries without validation or parameterisation, allowing an attacker to modify the query logic.

How it works #

The attacker inserts SQL code fragments into application input fields (login forms, search fields, URL parameters). If the application concatenates these inputs directly into SQL queries, the malicious code is executed by the database with the application user’s privileges. Combined with MySQL’s FILE privilege and an unconfigured secure-file-priv, the attacker can read system files or write arbitrary files on the server.

What it’s for #

Understanding SQL injection is fundamental for anyone managing databases in production, because many security configurations (such as secure-file-priv, privilege management and user separation) exist specifically to mitigate the impact of this type of attack.

When to use it #

The term describes an attack to prevent, not a technique to use. The main countermeasures are: parameterised queries (prepared statements), input validation, principle of least privilege for database users, and correct configuration of directives like secure-file-priv.