Ionic 4 Access-Control-Allow-Origin error

I’m using Mazemap from www.mazemap.com and getting the Access-Control-Allow-Origin error on both the browser and mobile devices.

The Mazemap interface does not provide an option for me to set the headers of the http request that it makes.

Is there a way in Ionic 4 to set the default headers of all http requests globally, or else how do I avoid this CORS error?