Which of the following is a major disadvantage of using unvalidated inputs in software?

Using unvalidated inputs in software poses a significant disadvantage because it can create security vulnerabilities such as command injections. When an application accepts input without proper validation, it becomes susceptible to a variety of attacks where malicious users can manipulate the input to execute harmful commands, access forbidden areas of the system, or disrupt the normal functioning of the application.

In the context of software security, validated inputs are essential for maintaining control over what data can be processed. When inputs are not validated, attackers can exploit this weakness to inject arbitrary commands or scripts, compromising the application's integrity and the underlying system. This can lead to data breaches, data corruption, or unauthorized access to sensitive information.

The other options do not reflect the inherent risks associated with unvalidated inputs. While it might seem that unvalidated inputs could simplify coding or improve performance, these perceived benefits are greatly outweighed by the potential security risks. Ensuring data integrity and security is paramount in software development, making input validation a crucial practice in protecting applications from vulnerabilities.