The polyfill.js is a popular open source library to support older browsers. 100K+ sites embed it using the cdn.polyfill.io domain. Notable users are JSTOR, Intuit and World Economic Forum. However, in February this year, a Chinese company bought the domain and the Github account. Since then, this domain was caught injecting malware on mobile devices via any site that embeds cdn.polyfill.io. Any complaints were quickly removed (archive here) from the Github repository.
It takes 2 clicks to get a website to work. It took a few minutes for me to get all my most commonly visited websites to work. And you can backup and restore so it takes a few minutes to sync the customization to all devices.