Fabian Keil - 2017-01-08

AFAIK nobody is currently working on proxy authentication
support. It's not on the TODO list either:
http://ijbswa.cvs.sourceforge.net/viewvc/ijbswa/current/TODO

My impression is that Privoxy users who need a certain kind of
proxy authentication put a proxy that supports it in front
of Privoxy.

I personally don't need proxy authentication and am unlikely
to work on implementing it in the near future (unless the work
is funded, of course).