Trying to pass a variable to report.html

Hi there!

I followed the discussions about customizing report.html and printing variables. Unfortunately I am not able to manage this.

I have texfields for the user to type in answers. The values are stored in variables. Now I try to send these variables to the report.html by:

var player=window.opener.GetPlayer();
var textExtry1 = player.GetVar("textExtry1");

But this doesn't work. I get Javascript-Errors:

Uncaught DOMException: Permission denied to access property "GetPlayer" on cross-origin object

or the message that "GetVar" was not defined and the report.html page is emtpy.

What is wrong... could anybody provide a suggestion?
Thank you so much!