[wplug-internet] Spam Attack?

[DK]

I have received two messages from Mailman, addressed to
postmaster at wplug.org, indicating that a message to "wplug" is awaiting
moderation.

Message body as follows:

Your mail to 'wplug' with the subject

   Mail System Error - Returned Mail

Is being held until the list moderator can review it for approval.

The reason it is being held:

   Post by non-member to a members-only list

Either the message will get posted to the list, or you will receive
notification of the moderator's decision.  If you would like to cancel
this posting, please visit the following URL:

   http://www.wplug.org/mailman/confirm/wplug/97feb94b471ecf0b4e6351c883c5f72d2b51f6d2

End:

The URL returns a bad confirmation string.  Anyone have an idea as to
what is going on?

Dave