To work around a browser bug (see T70537: In production, sometimes page scrolling stops working and in the console getting "Error: offset was inside a handlesOwnChildren node" in Firefox), we added .ve-ce-focusableNode * { -moz-user-select: none; }. The browser bug this was working around ( https://bugzilla.mozilla.org/show_bug.cgi?id=1132768 ) is fixed in FF39, but a different browser bug we were exploiting to be able to do this workaround ( https://bugzilla.mozilla.org/show_bug.cgi?id=1097242 ) was also fixed in FF39. Currently FF38 seems to be the latest stable version; when FF39 comes out (or ideally, before then) we should check if the fix for the second bug breaks our workaround for the first bug.