In djblets, we reference cdnjs.cloudflare.com to load things like jquery and

backbone (with the idea being that we don't want to have to ship things twice,

and users of djblets can override this if they don't want to use the CDN). In

Review Board, we had overrides for jquery and jquery-ui in order to load the

ones that we ship. However, we didn't have these overrides for underscore and

backbone. This was only visible in the extensions pages in the admin, which

use those templates to load the lib js. Most Review Board pages load underscore

and backbone through the normal bundles.

Loaded the extension list and saw that it was loading local copies of

underscore and backbone rather than CDN ones.