With Subresource Integrity (SRI), using GitHub is safer than ever. SRI tells your browser to double check that our Content Delivery Network (CDN) is sending the right JavaScript and CSS to your browser. Without SRI, an attacker who is able to compromise our CDN could send malicious JavaScript to your browser. To get the benefits of SRI, make sure you're using a modern browser like Google Chrome.
New browser security features like SRI are making the web a safer place. They don't do much good if websites don't implement them though. We're playing our role, and encourage you to consider doing the same.
You can read more about Subresource Integrity and why we implemented it on the GitHub Engineering blog.