Examine source code of URL Guardian

{
  "manifest_version": 2,
  "name": "URL Guardian",
  "version": "1.0",
  "description": "URL Guardian is a lightweight Firefox add-on designed to enhance your online safety. It actively monitors and alerts you when you are about to visit a URL that contains the '@' character and ends with '.zip' or '.mov' - a pattern that could potentially be dangerous. With URL Guardian, surf the internet with an added layer of protection and peace of mind.",
  "icons": {
    "48": "icons/warning.png"
  },
  "permissions": [
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "web_accessible_resources": [
    "warning.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{591d5841-36ca-49b0-9ce6-3e0b97a5fec0}"
    }
  }
}