Fetch Metadata Makes Cross-Site Request Context Visible
Fetch Metadata Makes Cross-Site Request Context Visible A server receiving an authenticated HTTP request often sees valid cookies, a plausible path, and a method that the application accepts. Those facts do not reveal whether the request began inside the application’s own page or was triggered by a document on another site. For endpoints that change state, that missing context has long been central to cross-site request forgery defenses. Fetch Metadata request headers expose part of the context already known to the browser. Headers such as Sec-Fetch-Site, Sec-Fetch-Mode, Sec-Fetch-Dest, and Sec-Fetch-User describe relationships and properties surrounding a request. A server can use those signals to reject request patterns that do not belong to its application architecture.