Which type of response header is effective in securing resources against certain cross-origin scripting attacks?

The Cross-Origin Opener Policy (COOP) is an effective response header for securing resources against certain cross-origin scripting attacks. COOP helps mitigate potential attacks by controlling the context in which documents can interact with each other. By setting a COOP header, a web application can prevent unintended interactions between itself and potentially malicious documents from different origins.

When COOP is implemented, it ensures that a browsing context (like a tab or an iframe) is isolated from other browsing contexts. This means that if one document is compromised, it cannot access information from a document with a different origin, thus protecting sensitive data and preventing exploitation of vulnerabilities such as cross-origin information leakage.

In the context of web security, employing COOP is particularly significant as it supports resilience against attacks that leverage cross-origin communications, such as window manipulation and data theft, thereby contributing to a more secure web environment.

Other options play various roles in securing web applications, but COOP specifically addresses the interaction and potential exploitation risks associated with cross-origin contexts, making it the most directly effective choice when dealing with scripting attacks in a cross-origin environment.