SQL Injection

June 1, 2023

SQL Injection is a type of security vulnerability prevalent in web applications that depend on user input to construct SQL queries dynamically. Attackers can exploit this vulnerability by injecting malicious SQL code into the application’s database, which could allow them to execute arbitrary SQL commands, and potentially access, modify, or delete sensitive data.


The objective behind SQL Injection attacks is to exploit weak spots in web applications that fail to validate user input adequately. Attackers can inject malicious SQL code into an application’s database to access confidential data, modify or delete data, execute arbitrary SQL commands, and even potentially compromise authentication and authorization systems. They can potentially steal sensitive information like credit card numbers or personal data, or even gain control over entire web servers.


SQL Injection attacks leverage specially crafted SQL statements, which are constructed to exploit vulnerabilities in a web application’s input validation routines. These statements range from simple data extraction queries to more complex commands that modify or delete data or even create new user accounts with administrative rights.

The most common technique of initiating SQL Injection attacks involves inputting malicious SQL code into web application input fields like login forms, search boxes, or comment fields. If the web application does not validate or sanitize user input adequately, the database server can execute the harmful code, which may provide the attacker access to sensitive data.

SQL Injection attacks can also be executed by manipulating the HTTP request parameters passed to a web application. By modifying the values of these parameters to include malicious SQL code, an attacker can trick the database server into executing these commands when the web application processes the request.


Preventing SQL Injection attacks involves secure coding practices and proper security technologies. Here are some of the critical practices:

Input Validation and Sanitization

Web applications should validate and sanitize all input data to ensure that it is safe and free from harmful content. This includes validating user input to ensure it conforms to expected formats and ranges and sanitizing input to remove any potentially malicious content such as SQL commands or HTML tags.

Parameterized Queries

Parameterized queries can be effective in preventing SQL Injection attacks by separating SQL code from user input data. Parameterized queries use placeholders for user input data, which are replaced with safe values during execution. This prevents user input data from being executed as SQL code, even if it contains malicious content.

Example of a parameterized query in PHP:

$stmt = $pdo->prepare('SELECT * FROM users WHERE email = :email');
$stmt->execute(['email' => $input]);

Least Privilege

Web applications should adhere to the least privilege principle, meaning they should only access the minimum amount of data and functionality required to perform their tasks. This can limit the potential damage from SQL Injection attacks, as attackers will only have access to a limited subset of the database.


Encryption of sensitive data like passwords and credit card numbers, both in transit and at rest, is crucial. It prevents attackers from accessing this data, even if they manage to exploit SQL Injection vulnerabilities.

Web Application Firewalls

Web Application Firewalls (WAF) can also be instrumental in preventing SQL Injection attacks. WAFs monitor incoming traffic to a web application and can block traffic that seems to be malicious, including traffic containing SQL Injection attacks.

To conclude, SQL Injection is a severe security vulnerability that can lead to significant data breaches if not appropriately managed. By implementing robust security measures, such as input validation, parameterized queries, least privilege principle, encryption, and using Web Application Firewalls, the risk associated with SQL Injection attacks can be significantly mitigated.