Command Injection is a type of security vulnerability that occurs when an attacker is able to execute arbitrary commands on a server or system through a vulnerable application. This typically happens when user input is not properly validated or sanitized, allowing malicious commands to be injected into the system. When successful, Command Injection can lead to unauthorized access, data theft, or even complete control over the affected system. To prevent this vulnerability, developers should implement strict input validation, use secure coding practices, and employ tools that can detect and mitigate such risks.