Examine source code of MacriGato

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "name": "Macri Gato",
  "version": "1.0.9resigned1",
  "manifest_version": 2,
  "description": "Cambia “Mauricio Macri” por “Macri Gato” cada vez que aparece.",
  "homepage_url": "http://macrigato.com.ar",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "js": [
        "inject.js"
      ],
      "matches": [
        "*://*/*"
      ],
      "exclude_matches": [
        "*://developer.mozilla.org/*",
        "*://*.macrigato.com.ar/*"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_action": {
    "default_title": "Macri Gato",
    "default_icon": "icon48.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{54aa27d3-b8c8-4f5a-9874-71c93b4a585a}"
    }
  }
}