Set permissions based on source viewer

I'd really like to be able to allow/deny access to a layer based on the place where the request is triggered. Not sure if this is remotely possible, but I'd like to deny access, unless a request comes from a certain VertiGIS Web viewer. Something like

if (!request.path.includes("app={appID}")) {
  denyTask("edit");
}

..but then instead of request.path it should be based on the path from where the request is sent.