Understanding OWASP top 10 v2021: A03: Injection

A03: Injection is one of the categories in the OWASP Top 10, which is a list of the most critical web application security risks. Injection vulnerabilities are a prevalent and dangerous type of security issue in web applications.

**Definition**:

Injection refers to a class of security vulnerabilities that occur when an attacker can manipulate or inject malicious data into an application's inputs, causing the application to execute unintended and potentially harmful commands. The most common types of injection attacks include SQL Injection (SQLi) and Cross-Site Scripting (XSS), but other forms, like Command Injection and NoSQL Injection, can also occur.

**Common Examples**:

1. **SQL Injection (SQLi)**: Attackers insert malicious SQL queries into input fields, often in forms, to manipulate or extract data from the application's database. This can lead to data theft, unauthorized access, and even data loss or corruption.

2. **Cross-Site Scripting (XSS)**: In XSS attacks, attackers inject malicious scripts (usually JavaScript) into web pages that are then executed by users' browsers. This can lead to session hijacking, stealing cookies, defacement, data exfiltration or other malicious actions.

3. **Command Injection**: This occurs when untrusted user input is used as part of a system command. Attackers can execute arbitrary commands on the server, potentially taking control of the system or other malicious actions.

4. **XML Injection**: Attackers inject malicious XML content into an application's XML parser, which can lead to denial of service, data leakage, or even remote code execution.

5. **NoSQL Injection**: Similar to SQL Injection but specific to NoSQL databases. Attackers manipulate queries to retrieve or modify data in unauthorized ways.

**Impact**:

The impact of injection vulnerabilities can be severe, ranging from data breaches and unauthorized access to the complete compromise of a system. Attackers can steal sensitive data, manipulate data, execute arbitrary code, and potentially gain control over the affected application or server.

**Mitigation**:

To prevent injection vulnerabilities, consider the following best practices:

1. **Parameterized Queries**: Use parameterized queries or prepared statements when interacting with databases. This prevents SQL Injection by treating user input as data, not executable code.

2. **Input Validation** and ***Input Sanitization***: Implement strict input validation to ensure that user-supplied data conforms to expected formats and content.

3. **Output Encoding**: Encode user-generated content before rendering it in web pages to prevent XSS attacks. This ensures that user input is treated as data, not executable code.

4. **Web Application Firewalls (WAFs) and Runtime Protection or Runtime Application Self Protection (RASP)**: Deploy, configure and enable injection blocking policies on a WAF & RASP to filter out malicious input and traffic before it reaches your application.

5. **Least Privilege**: Limit the privileges of application components and users to reduce the potential impact of an injection attack.

6. **Security Testing**: Conduct regular security testing, including Static Application Security Testing, Dynamic Application Security Testing, Software Composition Analysis, Infrastructure as Code Testing, Container Security Testing, Cloud Native Security Testing, manual and automated penetration testing and code reviews, to identify and remediate injection vulnerabilities.

7. **Content Security Policy (CSP)**: Implement CSP headers to mitigate the risk of XSS attacks.

8. **Security Awareness**: Train developers and users to be aware of injection vulnerabilities and how to prevent them.

Preventing injection vulnerabilities is crucial for maintaining the security of web applications. By following best practices and staying informed about the latest security threats, you can significantly reduce the risk of injection attacks.