18:23 UTC - We have determined that this issue is occurring due to an incident being experienced at our upstream provider. At 18:10, they acknowledged an incident causing 404 errors. At 18:17, they determined that the issue was partially resolved. More information can be found on our upstream provider's status website.
18:00 UTC - We are investigating an issue affecting the static assets (JavaScript and CSS files) of some sites. This issue is causing the affected sites not to load properly. As soon as more information becomes available, we will update this post.