You need to add a plugin and a configuration to work this arround:
cordova plugin add cordova-plugin-whitelist
Add this to your config.xml in the root of the ionic project:
<allow-intent href="*" />
<allow-navigation href="*" />
My Problem was:
I was not able to communicate with my NodeJS (Express) Backend within a normal AngularJS HTTP connection.
Also in the app included youtube videos could not be played.