Examine source code of ff.mail.ru

{
  "manifest_version": 2,
  "name": "ff.mail.ru",
  "version": "1.12",
  "description": "Kill add DIV",
  "icons": {
    "48": "icons/border-48.png"
  },
  "applications": {
    "gecko": {
      "id": "ff.mail.ru@mail.ru",
      "strict_min_version": "89.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.mail.ru/*"
      ],
      "js": [
        "ff.mail.ru.js"
      ]
    },
    {
      "matches": [
        "*://autoreview.ru/*",
        "*://*.autoreview.ru/*"
      ],
      "js": [
        "ff.autoreview.ru.js"
      ]
    },
    {
      "matches": [
        "*://*.f1news.ru/*"
      ],
      "js": [
        "ff.f1news.ru.js"
      ]
    },
    {
      "matches": [
        "*://*.avito.ru/*"
      ],
      "js": [
        "ff.avito.ru.js"
      ]
    }
  ]
}