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.
I don’t think we have to choose. “Maintain your websites so you don’t get taken advantage of” and “Here’s an example of a major-world-power-affiliated group exploting that thing you didn’t do” are both pretty important stories.