Via the Phpwiki 1.3.x UpLoad feature some hackers from russia uploaded a php3 or php4 file,
install a backdoor at port 8081 and have access to your whole disc and overtake the server.

A url in the file is http://ccteam.ru/releases/c99shell 

The uploaded file has a php, php3 or php4 extension and looks like a gif to the mime magic.
So apache usually accepts it.

To fix this phpwiki issue at first move the lib/plugin/UpLoad.php file out of this directory.

You can fix it by adding those two lines to your list of disallowed extensions:
  php3
  php4
Currently only "php" is disallowed.