The flexbox bugs: https://bugzilla.mozilla.org/buglist.cgi?quicksearch=flexbox+slow https://bugzilla.mozilla.org/buglist.cgi?quicksearch=flexbox... E.g., "Fire

The flexbox bugs: https://bugzilla.mozilla.org/buglist.cgi?quicksearch=flexbox+slow https://bugzilla.mozilla.org/buglist.cgi?quicksearch=flexbox... E.g., "Firefox slow to the point of hanging when rendering nested flexbox layout with overflow-y: scroll", which is trivial to reproduce, and which all other modern browsers handle fine. In fact, anybody who visits our product's site using Firefox is given a warning to use any other browser: https://github.com/sagemathinc/smc/issues/1314 https://github.com/sagemathinc/smc/issues/1314