Hi - due to the Chinese buying polyfill.io domain I was wondering would this have a security risk to Umbraco CMS - 8 and 13? Looking for Polyfill on our CMS 8 it comes up in the Umbraco services etc. We haven't used it ourselves but it looks like it is in the Umbraco side of things.

Is it the static files or is it used as a CDN link? I think if it is the former it should be ok. But the latter is where the problem lies.

No we never used polyfill.io. A polyfill is a generic term > Polyfills allow web developers to use an API regardless of whether or not it is supported by a browser, and usually with minimal overhead. https://en.wikipedia.org/wiki/Polyfill_(programming)