This server release fixes some permission bypass exploits.

You can grab the server from the downloads page.

Full Changelog below:
=== Server Release 3.5.1 18 December 2018
Fixed: Exploits that allowed to bypass permission checks.
       The exploits allowed to gain talk power and channel commander temporarily,
       to set their own avatar and client descriptions,
       and made it possible to prevent a client ban.
For discussion & feedback please use this thread.