If I've got it right, I created the initial post by hitting the "create" button (as per normal), then immediately decided that I wanted to make a minor change (ie replace "This malware" with "This upstream malware").
So ... I made that change and hit the "update" button that was sitting there. But instead of updating my initial post, a second almost-identical post was created.
(I then altered the subject line of the initial post to indicate that it should be reaped.)

Cheers,
Rob