core-bundle/src/Cors/WebsiteRootsConfigProvider.php
private function isCorsRequest(Request $request): bool
    {
        return $request->headers->has('Origin')
            && $request->headers->get('Origin') !== $request->getSchemeAndHttpHost()
        ;
    }
private function isCorsRequest(Request $request): bool
    {
        return $request->headers->has('Origin')
            && $request->headers->get('Origin') !== $request->getSchemeAndHttpHost()
        ;
    }
Checks if the request has an Origin header.