17-year old, Mikkey Mooney, has claimed responsibility and has stated he is the person behind the twitter worm the past few days:
“I am the person who coded the XSS which then acted as a worm when it auto updated a users profile and status, which then infected other users who viewed their profile. I did this out of boredom, to be honest. I usually like to find vulnerabilities within websites and try not to cause too much damage, but start a worm or something to give the developers an insight on the problem and while doing so, promoting myself or my website.
I decided if I had a site that followed the same functionality and simplicity as one of the most known sites on the web at the time then it would receive a lot of hits. While playing around and getting the site developed I started adding more features and tried to part myself from Twitter, while still giving it’s still compact nature and simple use.
Only the sessions were encrypted and passwords were not played with, so it was not that harmful, but was still a matter of concern and the Twitter team was able to resolve that pretty fast."
Techstartups advice to all users: If your Twitter ID is compromise immediately change your password!
Protect your information or he'll take it away.