The existence of a “feature” that relies on UA strings being consistent across domains, with the potential to “brick YouTube entirely in a user-visible way for all Firefox 43 users in Europe”[1], is quite worrying to be honest.<p>[1] <a href="https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1233970#c61" rel="nofollow">https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1233970#c61</a>