Examine source code of InspiroFox

{
  "background": {
    "page": "background.html"
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "description": "See a new Inspirobot poster every time you open a tab.",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "manifest_version": 2,
  "name": "Inspirotab",
  "permissions": [
    "tabs",
    "https://inspirobot.me/"
  ],
  "version": "1.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "{913ccffa-8efc-41db-9b65-a291f8b944ab}"
    }
  }
}