Third-party script loading is as old as the <script> tag and predates any applicable standards. That is, browsers added <script> before standards did, and allo

Third-party script loading is as old as the <script> tag and predates any applicable standards. That is, browsers added <script> before standards did, and allowed cross-site loading of scripts, just like cross-site loading of everything was allowed at that point. Simpler days, 25 years ago...