The webserver listening on localhost:19421 should [...] set a[n] Access-Control-Allow-Origin header with the value https://zoom.us https://zoom.us. This will en

The webserver listening on localhost:19421 should [...] set a[n] Access-Control-Allow-Origin header with the value https://zoom.us https://zoom.us. This will ensure that only Javascript running on the zoom.us domain can talk to the localhost webserver. If you create a single-purpose webserver, you can really handle this better than asking the client to play nice via an HTTP header.