OS Command Injection is a cybersecurity vulnerability that occurs when an attacker is able to trick a system into executing unauthorized operating system commands. This happens when a web application or software improperly handles user input, allowing malicious commands to be passed to the underlying OS. As a result, attackers may gain control over the system, access sensitive data, or disrupt normal operations. Preventing OS Command Injection requires careful input validation and secure coding practices to ensure user input cannot affect system commands.