SQL injection (SQLi) is a type of web application security vulnerability that allows attackers to inject malicious SQL code into a database. This can lead to: 1. Unauthorized data access 2. Data theft 3. Data manipulation 4. System compromise How SQL injection works: 1. Attackers find vulnerabilities in user input fields. 2. They inject malicious SQL code. 3. The database executes the code, revealing or modifying sensitive data. Types of SQL injection: 1. Classic SQL injection 2. Blind SQL injec