Still at 18.
I'm told not everybody knows this page with instructions about backport
to stable releases:
<https://www.mediawiki.org/wiki/Backporting_fixes#Backports_to_stable.2Fsupported_release>
Most of those bugs still need patches to baked up rather than backports,
but please do remember to flag (in a way or another) the bugs which you
think (will) need backporting to stable. Too often they're marked fixed
in master and forgotten, for instance.
Nemo