The list admin or moderator password can be compromised by sending in an Approved: header

[Mark Sapiro]

If posting to a list is secured by requiring an Approved: or X-Approved: header for a post to be accepted without moderation, the list admin or moderator password can be compromised by sending it in the headers of an email message.

There should be a 'poster' password for this purpose only so the consequences of compromise would be less severe.