Examine source code of Shopper.com

{
  "name": "__MSG_extName__",
  "description": "__MSG_extDescription__",
  "homepage_url": "https://www.shopper.com/?source=plugin",
  "default_locale": "en",
  "background": {
    "persistent": true,
    "page": "background.html"
  },
  "browser_action": {
    "default_icon": {
      "16": "images/default_icon_16.png",
      "32": "images/default_icon_32.png"
    },
    "default_title": "__MSG_extDefaultTitle__"
  },
  "content_scripts": [
    {
      "all_frames": false,
      "js": [
        "js/browser-polyfill.js",
        "js/jquery.js",
        "js/install.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_start"
    },
    {
      "all_frames": false,
      "css": [
        "css/content.css",
        "css/popup.css"
      ],
      "js": [
        "js/config.js",
        "js/shoppers.js",
        "js/content.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_end"
    }
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "icons": {
    "16": "images/active_icon_16.png",
    "32": "images/active_icon_32.png",
    "48": "images/active_icon_48.png",
    "120": "images/active_icon_120.png",
    "128": "images/active_icon_128.png"
  },
  "permissions": [
    "activeTab",
    "cookies",
    "storage",
    "unlimitedStorage",
    "http://*/*",
    "https://*/*"
  ],
  "version": "4.3.22",
  "manifest_version": 2,
  "short_name": "Shopper.com",
  "web_accessible_resources": [
    "images/*",
    "iframes/*",
    "css/*",
    "js/jquery.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{541068b2-3c8c-4c52-89a7-ef2c4ddc1244}"
    }
  }
}