A:SQL injection is a type of attack that allows an attacker to gain unauthorized access to a database by exploiting vulnerabilities in an application's code. This type of attack is possible when an application uses user-supplied data in SQL queries without properly validating or sanitizing the data. By exploiting these vulnerabilities, an attacker can gain access to sensitive data, modify or delete data, or even execute system commands on the server. To prevent this type of attack, developers must ensure that all user-supplied data is properly validated and sanitized before being used in SQL queries.