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:

<access origin="*"/>
<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.