Your version of Squid is not supported by Webmin. Only versions from 1.1 to 3.4 are supported by this module.
The command squid -v returned :
Squid Cache: Version 3.5.2
Service Name: squid
configure options: '--prefix=/usr' '--localstatedir=/var' '--libexecdir=/lib/squid' '--srcdir=.' '--datadir=/share/squid' '--sysconfdir=/etc/squid' '--with-default-user=proxy' '--with-logdir=/var/log' '--with-pidfile=/var/run/squid.pid' '--with-openssl'
i am having this message when trying to access the webmin: Your version of Squid is not supported by Webmin
It's fixed in the git version. It will be added to the next release.
You could apply the patch manually by editing
squid/index.cgi
file and replacing it with this (not first 3 lines):https://raw.githubusercontent.com/webmin/webmin/95ab22916ff80eeb80225ef6de20a6307ad97bd0/squid/index.cgi
The current version of Webmin hasn't been tested with Squid 3.5, but I will add this for the next release.
Alternately, the 1.894 devel version of Webmin from http://www.webmin.com/devel.html includes this fix.