As of the 20th of December 2016, Fedora 23 has reached its end of life
for updates and support. No further updates, including security
updates, will be available for Fedora 23. A previous reminder was sent
on 28th of November 2016 . Fedora 24 will continue to receive
updates until approximately one month after the release of Fedora 26.
The maintenance schedule of Fedora releases is documented on the
Fedora Project wiki . The Fedora Project wiki also contains
instructions  on how to upgrade from a previous release of Fedora
to a version receiving updates.