CVE-2026-70604: Electron: Custom protocol with supportFetchAPI but not corsEnabled allows cross-origin reads

A custom scheme registered with supportFetchAPI: true but without corsEnabled: true was not subject to CORS enforcement. A page loaded from a remote origin could therefore fetch() or XMLHttpRequest that scheme cross-origin and read the full response body, rather than the read being blocked.

Apps that serve sensitive data from such a scheme and load remote or untrusted content in a renderer are affected. Apps that set corsEnabled: true, or that do not load untrusted content, are not affected.