I don't think this qualifies as a bug. Using the wrong client is user error. fingerd should not be responsible for filtering anything you shouldn't send it.
Index: fingerd.8 =================================================================== RCS file: /cvs/src/libexec/fingerd/fingerd.8,v retrieving revision 1.19 diff -u -p -r1.19 fingerd.8 --- fingerd.8 14 Nov 2013 08:50:04 -0000 1.19 +++ fingerd.8 20 Nov 2014 03:31:21 -0000 @@ -166,18 +166,3 @@ The .Nm command appeared in .Bx 4.3 . -.Sh BUGS -Connecting directly to the server from a -.Tn TIP -or an equally narrow-minded -.Tn TELNET Ns -protocol -user program can result -in meaningless attempts at option negotiation being sent to the -server, which will foul up the command line interpretation. -.Nm -should be taught to filter out -.Tn IAC Ns 's -and perhaps even respond -negatively -.Pq Tn IAC WON'T -to all option commands received.
