Examine source code of View Server

{
  "manifest_version": 2,
  "name": "View Server",
  "description": "This extension uses the 'Server' and 'X-Powered-By' headers to determine the current site's server software",
  "version": "1.3.2resigned1",
  "icons": {
    "16": "/icon/icon16.png",
    "32": "/icon/icon32.png",
    "48": "/icon/icon48.png",
    "64": "/icon/icon64.png",
    "128": "/icon/icon128.png"
  },
  "browser_action": {
    "default_title": "View Server",
    "default_icon": {
      "19": "/icon/icon19.png",
      "38": "/icon/icon38.png"
    },
    "default_popup": "/popup/view_server.html"
  },
  "background": {
    "scripts": [
      "/third_party/browser-polyfill.min.js",
      "/background_scripts/save_server_headers.js"
    ],
    "persistent": true
  },
  "permissions": [
    "tabs",
    "webRequest",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f41d5e9c-2b66-490c-8eab-3daeefd9077e}"
    }
  }
}