Examine source code of Device Privacy

{
  "manifest_version": 2,
  "name": "Privacy",
  "version": "2.0.0",
  "icons": {
    "32": "icon.svg",
    "64": "icon.svg"
  },
  "description": "Remove all information about your device and browser",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "injector.js"
      ],
      "run_at": "document_start"
    }
  ],
  "background": {
    "scripts": [
      "headers.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "scripting",
    "activeTab",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a60aff17-d4c2-4683-a69c-8866bb06df4b}"
    }
  }
}