Examine source code of Maskmail

{
  "manifest_version": 2,
  "name": "Maskmail",
  "description": "This extension uses Maskmail.net to hide your email from online trackers",
  "version": "5.2resigned1",
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "app/index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*",
        "http://localhost/*"
      ],
      "exclude_matches": [
        "https://*.happybun.com/*",
        "https://happybun.com/*",
        "https://*.maskmail.net/*",
        "https://maskmail.net/*"
      ],
      "js": [
        "clipboard.js",
        "frameActions.js",
        "content.js"
      ],
      "all_frames": true
    },
    {
      "matches": [
        "https://maskmail.net/dashboard",
        "https://www.maskmail.net/dashboard"
      ],
      "js": [
        "frameActions.js",
        "clearLocalCache.js"
      ],
      "all_frames": true
    }
  ],
  "web_accessible_resources": [
    "app/index.html"
  ],
  "permissions": [
    "activeTab",
    "<all_urls>",
    "https://maskmail.net/",
    "http://localhost:3004/",
    "https://happybun.com/",
    "https://api.rollbar.com/",
    "clipboardRead",
    "clipboardWrite",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{fa5c8ec5-a099-4b62-a89c-45f714f1fba8}"
    }
  }
}