I\'m using an angular2 front end and WebApi backend. The webapi is CORS enabled
var cors = new EnableCorsAttribute(\"*\", \"*\", \"*\"); GlobalConfiguration.
You can add one add-on in your Firefox browser. It will work in your firefox browser like charm. Cors Everywhere solved my problem. https://addons.mozilla.org/en-US/firefox/addon/cors-everywhere/