According to wikipedia.org;wiki is a type of website that allows visitors to easily add, remove, or otherwise edit and change some available content, sometimes without the need for registration, it is an editable website that does not require users to know HTML.

Reports on SANS Internet Storm Centre tell us of botnets being created with the use of Software bugs in Pmwiki and Tikiwiki software applications. According to them Pmwiki exploit is hitting versions 2.1.19 and below and Tikiwiki versions 1.9 and below.

The way the exploit on Pmwiki can be exploited is if you have “Register_globals” turned to “On” in your php installation. But, the Tikiwiki exploit is exploited regardless if the setting is On or Off.

Tikiwiki has published some information regarding this matter here. And Pmwiki has been said to have updated their code. Check the Release notes for more details