{
  "title": "Site Switcher",
  "name": "site-switcher",
  "version": "1.2.1",
  "description": "Easily switch across live, stage & local site",
  "main": "lib/index.js",
  "author": "Markus Popp",
  "icon": "icon.png",
  "engines": {
    "firefox": ">=45.0"
  },
  "license": "MIT",
  "keywords": [
    "jetpack"
  ],
  "preferences": [{
    "name": "sites",
    "title": "Sites JSON",
    "label": "Supported Sites",
    "description": "Supported Sites in JSON format",
    "type": "string"
  }],
  "permissions": {
    "private-browsing": true
  }
}

{
  "title": "Site Switcher",
  "name": "site-switcher",
  "version": "1.2.2",
  "description": "Easily switch across live, stage & local site",
  "main": "lib/index.js",
  "author": "Markus Popp",
  "icon": "icon.png",
  "engines": {
    "firefox": ">=52.0"
  },
  "license": "MIT",
  "keywords": [
    "jetpack"
  ],
  "preferences": [{
    "name": "sites",
    "title": "Sites JSON",
    "label": "Supported Sites",
    "description": "Supported Sites in JSON format",
    "type": "string"
  }],
  "permissions": {
    "private-browsing": true,
    "multiprocess": true
  }
}

Set multiprocess permission to true; require Fx52+
Set multiprocess permission to true; require Fx52+
