This just in! Twitter says the worm has been dealt with...
TIP: View Twitter Through Other People's Eyes With TwtRoulette H/T @techcrunch.
A powerful Twitter worm is circulating right now, affecting thousands of accounts, just days after the "OnMouseOver" hack hit hundreds of thousands. Christian Heilmann notes that this is a Twitter exploit. It creates a tweet with obscene language on your account, accompanied by a separate tweet that says "WTF" with a link. The link is wrapped in Twitter's URL shortener "t.co," and as others click it, the worm spreads.
The affected tweets are being tweeted via the "Tweet Button," and it is automatically generated on your account once you click the bad link.In just 15 lines of code, the worm creates a tweet with obscene language on your account. The code to execute the “worm” is hosted at http://pastehtml.com/view/1b7xk3b.html