Examine source code of Mturk Group ID

{
  "name": "Group ID",
  "version": "1.1",
  "description": "Adds group IDs to mturk iframes",
  "permissions": [
    "webNavigation",
    "tabs"
  ],
  "icons": {
    "48": "rp48.png",
    "128": "rp128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "*://worker.mturk.com/projects/*"
      ],
      "run_at": "document_start",
      "js": [
        "mturk.js"
      ]
    }
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{8a8f7c75-c81f-4dce-b171-5f0616ddcaee}"
    }
  }
}