Recently the image Great_Seal_of_the_United_States_(small).png vanished;
its image description page listed it as present and had a link to one
revision, but the image itself was gone.
After brief investigation, I found that the image file was still present
in the archives directory, and copied it back to where it belonged...
but there had also once been an earlier revision of the same file (a
non-transparent PNG), now missing both from the archive and the image page.
Grepping the access logs, it turned out that a spider had come across
the image description page and followed links to both revert and delete
the older revision of the image -- simply loading up these links caused
the wiki to move and permanently delete files.
Apparently telling it to both revert and delete the same revision
confused the poor wiki, and it ended up vanishing that revision entirely
_and_ leaving the newer one only in the archives.
As a workaround until a better way of handling these functions is
decided on, I've hacked Skin.php to not give the delete/revert links to
anonymous users (and therefore bots and spiders).
-- brion vibber (brion @
pobox.com)