SQL Injection

SQL Injection is one of the most common and dangerous web application security vulnerabilities. It is an attack technique where a malicious user inserts or 'injects' their own SQL code into an application's input fields (like a search bar or a login form). If the application's backend code is not properly written to handle this input, it might concatenate the user's malicious string directly into its own SQL query and execute it. This allows the attacker to bypass security measures and directly manipulate the application's database. For example, consider a login form that builds a query like this: `SELECT * FROM users WHERE username = '` + userInput + `' AND password = '` + passInput + `';`. An attacker could enter `' OR '1'='1` as their username. The resulting query would become `SELECT * FROM users WHERE username = '' OR '1'='1' AND ...`. Because `'1'='1'` is always true, the `WHERE` clause evaluates to true, and the query might return all users, effectively logging the attacker in without a valid password. A successful SQL injection attack can result in unauthorized viewing of sensitive data, modification or deletion of data, and even gaining administrative control over the entire database server. The primary way to prevent SQL injection is to never trust user input and to avoid dynamic query construction. Instead, developers must use 'prepared statements' (also known as parameterized queries), where the SQL query is sent to the database first, and the user input is sent separately as parameters. This ensures the input is treated as data, not as executable code.