Examine source code of ReadCube

{
  "author": "Readcube",
  "name": "ReadCube",
  "homepage_url": "https://www.readcube.com/",
  "manifest_version": 3,
  "description": "Easily import articles and webpages to your ReadCube library.",
  "action": {
    "default_title": "ReadCube",
    "default_icon": {
      "16": "img/icon16.png",
      "32": "img/icon32.png",
      "48": "img/icon48.png",
      "96": "img/icon96.png",
      "128": "img/icon128.png"
    }
  },
  "commands": {
    "open-web-app": {
      "suggested_key": {
        "default": "Ctrl+Shift+P",
        "windows": "Ctrl+Shift+P",
        "mac": "Command+Shift+P"
      },
      "description": "Open ReadCube web app"
    }
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "icons": {
    "16": "img/icon16.png",
    "32": "img/icon32.png",
    "48": "img/icon48.png",
    "96": "img/icon96.png",
    "128": "img/icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "inject.html"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "minimum_chrome_version": "93",
  "background": {
    "scripts": [
      "js/background.bundle.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.rightfind.com/*"
      ],
      "js": [
        "/iframeRightfind.js"
      ],
      "all_frames": true,
      "match_about_blank": true
    }
  ],
  "permissions": [
    "tabs",
    "storage",
    "activeTab",
    "cookies",
    "scripting",
    "webRequest"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{003fb763-c222-4734-9773-bc19ba823079}"
    }
  },
  "content_security_policy": {
    "extension_pages": "default-src 'self' https://staging.readcube.com/ https://www.readcube.com/ https://services-staging.readcube.com https://staging.readcube.com https://services.readcube.com https://www.readcube.com; script-src 'self'; connect-src * file:; style-src * 'unsafe-inline'; img-src 'self' https://media.readcube.com/ https://images.readcube.com/ https://objects.readcube.com/ https://s3.amazonaws.com/ data:; object-src 'self';"
  },
  "version": "6.12.0"
}