SQL Injection

SQL injection occurs when user input is concatenated directly into SQL queries.

How attacks work

• Attacker enters malicious SQL in input fields.
• Application executes the attacker's code against the database.
• Results can include data theft, deletion, or authentication bypass.

Example vulnerable code

SELECT * FROM users WHERE username = '$input';
-- Input: ' OR '1'='1
-- Result: SELECT * FROM users WHERE username = '' OR '1'='1';

Prevention

• Use parameterized queries (prepared statements).
• Validate and sanitize all user input.
• Apply principle of least privilege to database accounts.
• Implement web application firewalls (WAFs).