What attack involves manipulating the URL to access sensitive system files on a web server?

The attack that involves manipulating the URL to access sensitive system files on a web server is known as Directory Traversal. This type of attack exploits vulnerabilities in a web application by allowing an attacker to traverse the file system, often by using special character sequences (like "../") in the URL. By doing so, the attacker can potentially access directories and files that are outside the webroot folder, which would normally be restricted. This can lead to unauthorized access to sensitive files, such as configuration files, password files, or other critical data on the server.

Directory Traversal is particularly concerning because it can reveal internal server structures and lead to further exploitation or data breaches if sensitive information is accessed. It emphasizes the need for proper validation and sanitization of user inputs, as well as rigorous access controls on server directories.

The other options describe different types of attacks that do not focus on file system manipulation through URL alterations.