Disqus Chrome Extension Injection

cs.js

// We just need to check if the IFrame origin is from discus.com
if (location.hostname.indexOf('.disqus.com') != -1) {
  // Extract the textarea (there must be exactly one)
  var commentBox = document.querySelector('#comment');
  if (commentBox) {
    // Inject some text!
    commentBox.innerText = 'Google Chrome Injected!';
  }
}

manifest.json

{
  "name": "Disqus Inject",
  "version": "0.1",
  "description": "Disqus Inject",
  "content_scripts": [
    {
      "matches": ["http://*/*"],
      "js": ["cs.js"],
      "run_at": "document_end",
      "all_frames": true
    }
  ]
}