When trying to view a raw file (http://phabricator.install/file/info/PHID-FILE-uzurwewgs4q4n6guy22q/), I'm getting the following Unhandled Exception:

You are building a <form /> that submits to Phabricator, but has an absolute URI in its 'action' attribute ('http://phabricator.install/file/data/w2lp3bjvxw36jmqbpnii/PHID-FILE-uzurwewgs4q4n6guy22q/prod.sh'). To avoid leaking CSRF tokens, Phabricator does not add CSRF information to forms with absolute URIs. Instead, use a relative URI.

It works for some files (json, js, css - those that view directly) but fails for others (php, sh, twig - those that need to show the info - these are a bit random too, I'd have thought they could view directly)

A bit of digging shows PhabricatorEnv::getCDNURI($path) is returning the absolute URI in getViewURI()

I presume this is a configuration issue on our end since I can't reproduce on secure.phabricator.com, but I can't track down what's changed.
Any ideas?