Examine source code of Highlight Search Term is

{
  "manifest_version": 2,
  "name": "Highlight Search Terms",
  "version": "1.0",
  "description": "Automatically highlights search terms on the page from the referrer.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "<all_urls>",
    "webRequest",
    "webRequestBlocking"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{dabbc18f-8808-4c69-8a1f-e54adf6fceb4}"
    }
  }
}