Instead of enabling studies just click on this link. It installs that specific "study" (hotfix) without installing anything else. https://storage.googleapis.com/moz-fx-normandy-prod-addons/e...
Hold up there. Before people start clicking and installing random add-on links, how about linking to something official (either from a FF dev, or in a soure repository) that references this URL?
https://news.ycombinator.com/item?id=19825921
I'm not clear if they rehosted the XPI or if that's the original mozilla url.
I'm not too worried about it either. The only reason anyone is clicking on this fine link is because firefox only lets you install addons signed by Mozilla. And since the typical signing process gives addons signed by the broken intermediary we can be pretty confident that this wasn't just signed by mozilla, but is the original study.
In general caution about installing software from random links is definitely a good idea though.
Edit: Looks to me like it's an original mozilla url (judging by github comments on mozilla/normandy - I haven't found an official source saying it is official due to lack of continuing to search: https://github.com/mozilla/normandy/pull/1697)