How to change DOM elements loaded from iFrame from another server?

Question

JavaScript

I'm making a browser extension. There is a site example.com and the iFrame anather.example.com is loaded on it . I'm trying to get the element, it doesn't see it, I'm trying to get the document iFrame, I get: Blocked
script execution because the document's frame is sandboxed and the 'allow-scripts' permission is not set

. Who faced??? HELP!!

Corrected allow-script . I am making an analogue of the script, this feature is implemented on the same site.
I get a new error on with the same meaning.
Blocked a frame with origin " www.example.com " from accessing a cross-origin frame.

And I just need to add an element, in order to be able to read information from Dom elements on click.