Final answer:
SQL injection is a web application vulnerability where attackers manipulate SQL queries to gain unauthorized access to databases. Avoiding SQL injection involves using parameterized queries or prepared statements. A successful SQL injection attack can lead to actions like bypassing authentication, accessing sensitive data, and executing arbitrary commands.
Step-by-step explanation:
SQL injection is a type of web application vulnerability where an attacker can manipulate the SQL queries executed by the application, leading to unauthorized access to the database. The root cause of SQL injection is the lack of proper input validation and sanitization in the application code, which allows attackers to inject malicious SQL statements. To avoid SQL injection, developers should use parameterized queries or prepared statements, which separate the SQL code from user input and automatically escape special characters.
A successful SQL injection attack can allow the attacker to perform various malicious actions, such as bypassing authentication, accessing sensitive data, modifying or deleting data in the database, or even executing arbitrary commands on the underlying server. For example, an attacker could exploit a SQL injection vulnerability in a login form to bypass authentication and gain administrative privileges, giving them full control over the application.