Which response header changes the way documents load to prevent cross-origin attacks but would not be effective against XSS Inclusion attacks?

The correct response is the Cross-Origin Opener Policy (COOP). This HTTP response header is designed to enhance security by controlling how documents from different origins interact with each other, thereby providing protections against cross-origin attacks such as window access and data stealing when navigating between different origins. By establishing a stricter separation between origins, COOP can help mitigate risks associated with shared resources in scenarios where an application might be vulnerable to various attacks.

However, it is important to note that COOP specifically does not provide protection against all forms of Cross-Site Scripting (XSS) attacks. XSS attacks typically revolve around injecting malicious scripts into trusted web applications, and COOP does not address the core vulnerabilities that facilitate such injections. Tools and practices aimed at sanitizing inputs, using content security policies, and validating user inputs remain necessary to guard against XSS attacks effectively.

In contrast, the other options focus primarily on different security aspects, such as preventing frame embedding or controlling resource sharing and do not provide the same specific environment focus on interactions across origins.