they don't let you run in browser contexts normally but they definitely let you set your own new tab page(with webextension privileges) as part of the extension

they don't let you run in browser contexts normally but they definitely let you set your own new tab page(with webextension privileges) as part of the extension which lets an extension do whatever they want. see: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/chrome_url_overrides https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web... they also have most requested urls as a privilege too so it could be recreated and extended with a little effort.