Examine source code of wppsafe

{
  "manifest_version": 2,
  "name": "wppsafe",
  "version": "1.0.3resigned1",
  "description": "Esconda as imagens do WhatsApp Web e exiba somente quando quiser. Passe o mouse na imagem para exibi-la.",
  "content_scripts": [
    {
      "matches": [
        "*://web.whatsapp.com/*"
      ],
      "css": [
        "src/nsfw.css"
      ]
    }
  ],
  "icons": {
    "48": "icon/wppsafe-icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ac29b753-a1c6-45f1-8de6-ed858a319f96}"
    }
  }
}