The Firefox app has a direct reference to bits.wm.o encoded in its install.html here: https://github.com/wikimedia/apps-firefox-wikipedia/blob/master/install.html#L20
That, in turn, causes it to load the rest of the app from the same host/directory (bunch of js/image files, etc). We'd like to get that off of the bits hostname by uploading a new version of the app at some time, as the bits.wm.o hostname is slowly being deprecated now (but for this app and a host of other reasons, we'll probably have it available for backcompat long into the foreseeable future).
I'm not even sure what the replacement hostname or URL base path would look like, yet, and we'd still need to do some work to make it available at that future path. @ori may have some insight on that side of things.
Notable when researching this originally: The app store has version 3.2.9 as the latest. Our git repo has a handful of changes beyond that and a version bump to 3.3.0 dating back to mid-last-year, which was never pushed to the app store. Unsure if we'd want to include those changes, or just do a minimal update based on the 3.2.9 update to keep the risk down...
Assigning to @ori for now to look at where this should end up hostname/path -wise, can pass hot potato to @brion after :)