Examine source code of MailFail

{
  "manifest_version": 2,
  "name": "MailFail",
  "version": "1.0.21",
  "description": "Checks for flaws in the email security of the current domain",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "128": "icons/mailfail-128x128.png"
  },
  "browser_action": {
    "default_icon": {
      "128": "icons/mailfail-128x128.png"
    }
  },
  "permissions": [
    "notifications",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c35a6e9-fc70-488d-a6db-01f2974fa80e}"
    }
  }
}