Examine source code of Horizon

{
  "manifest_version": 2,
  "name": "Horizon",
  "version": "1.2resigned1",
  "author": "Vladan Tomic",
  "description": "Web application security testing tool for Firefox",
  "icons": {
    "48": "assets/horizon.svg"
  },
  "permissions": [
    "tabs",
    "activeTab",
    "webRequest",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "main.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "page.js"
      ]
    }
  ],
  "devtools_page": "devtools/devtools.html",
  "browser_action": {
    "default_icon": {
      "16": "assets/button-disabled.svg",
      "32": "assets/button-disabled.svg"
    }
  },
  "web_accessible_resources": [
    "assets/horizon.svg",
    "assets/button.svg",
    "assets/button-disabled.svg"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{52a11617-5b17-451b-9e73-2e76bf5af274}"
    }
  }
}