I plugged in some of the "search" strings at random to Google and there are thousands of reports of this type of activity, it does not appear to be targeted at dokuwiki, but any type of website. Some people have reported a Denial of Service with 20+ per second of this type of activity. I have not found a good explanation yet of what they appear to be trying to exploit.
For dokuwiki, the most common thing that I would expect is a POST with some sort of spamming or defacement, not a GET. Offhand, I would guess it is some type attempt at Buffer Overrun (BO) but I don't know what the actual target is.
Jonathan -- DokuWiki mailing list - more info at http://wiki.splitbrain.org/wiki:mailinglist
