docs: include warning on polyfillio sheet; use cf

polyfill.io.md

@@ -1,41 +1,45 @@
 ---
 title: Polyfill.io
 category: JavaScript libraries
-updated: 2018-08-20
+updated: 2024-06-26
 intro: |
-  [Polyfill.io](https://polyfill.io) is a service that serves JavaScript polyfills.
+  Polyfill.io is a service that serves JavaScript polyfills.
 ---
 
+> ⚠️ **CRITICAL SECURITY WARNING**
+>
+> The polyfill.io CDN domain is currently being used in a web supply chain attack and is serving malicious code. **Remove any references to this domain from your codebase immediately**. Use alternative CDN providers like cdnjs.cloudflare.com as shown in the examples below.
+
 ## Usage
 
 ### Default usage
 
 ```html
-<script src="https://cdn.polyfill.io/v2/polyfill.min.js"></script>
+<script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js"></script>
 ```
+
 {: .-wrap}
 
 This is the default script for Polyfill.io.
 
 ### References
 
-* [API example](https://polyfill.io/v2/docs/api) _(polyfill.io)_
-* [List of features](https://polyfill.io/v2/docs/features) _(polyfill.io)_
+* [Cloudflare now serves polyfill.io](https://blog.cloudflare.com/polyfill-io-now-available-on-cdnjs-reduce-your-supply-chain-risk) _(blog.cloudflare.com)_
 
 ## Optimized
 
 ### For modern browsers
 
 ```html
-<script>if(!(window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdn.polyfill.io/v2/polyfill.min.js"></scr'+'ipt>')}</script>
+<script>if(!(window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js"></scr'+'ipt>')}</script>
 ```
 
 This only includes polyfill.io when necessary, skipping it for modern browsers for faster load times.
 
 ### Extra features
 
 ```html
-<script>if(!(window.fetch&&window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=default,fetch"></scr'+'ipt>')}</script>
+<script>if(!(window.fetch&&window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js?features=default,fetch"></scr'+'ipt>')}</script>
 ```
 
 This is the same as the previous, but also adds a polyfill for `window.fetch()`. We add a `window.fetch` check and loads the additional `fetch` feature.