Password(s) stored on file(s) readable by anyone

[Alvaro Uria]

update_password write a file with default perms (generally, 644). Password should be stored on a file with perms 0400.
"""
nagios-1:~$ ls -l /var/lib/juju/nagios.*
-rw-r--r-- 1 root root 12 Nov 21 15:26 /var/lib/juju/nagios.nagiosadmin.passwd
-rw-r--r-- 1 root root 12 Nov 21 15:26 /var/lib/juju/nagios.nagiosro.passwd
-r-------- 1 root root 11 Aug 2 22:53 /var/lib/juju/nagios.passwd
"""

https://git.launchpad.net/nagios-charm/tree/hooks/upgrade-charm#n332