In a web extension, is it possible to fetch content from one of Firefox's about pages? e.g about:addons or about:downloads

In order to scrape or parse the DOM.

Current attempt below ..

Error:

Security Error: Content at 
moz-extension://b6bc9d62-712c-104a-b53a-95ae7a02487d/_generated_background_page.html 
may not load or link to about:addons.

manifest.json

{
  "name": ..
  "permissions": ["notifications", "activeTab", "nativeMessaging"],
  "background": {"scripts": ["backgroundScript.js"]},
  ..
}

backgroundScript.js:

var x = new XMLHttpRequest();
x.onload = function() {
  console.log(x.responseText);
};
x.open('GET', 'about:addons');
x.send();