Recently, I talked about getting an error in my mailbox instead of the notification email from Webmin 1.5’s Software Package Update module. Today, I found a hint to its solution on the sourceforge.net email archives.
This is a known bug and it will be fixed in next public release, if you don’t wish to wait, you can do a devel-update of your webmin.

[…] A fix is available for this bug Share […]
Manual fix:
Date: 2009-12-10 18:37
Sender: jcameron
Thanks – there’s a typo in that script. Line 12 of
/usr/local/webmin-1.500/package-updates/update.pl should read :
@current = &list_current(1);
From comment on:
http://sourceforge.net/tracker/index.php?func=detail&aid=2912059&group_id=17457&atid=117457