It's one of these days where I just had one of these "Oh no..." moments when I logged into my Twitter account and suddenly a message box with my cookie popped up.
Update 3 (14:24 CEST): Worm code for this vulnerability has been posted on IRC, making the rounds.
Update 4 (14:36 CEST): Worm is live already...
Update 5 (14:59 CEST): It appears Twitter now properly escapes links, that specific vulnerability seems closed.
Update on Infection Rates (posted by Costin): During the peak of the infection, we noticed roughly 100 posts per second which seemed to be related to the exploit. Thanks to Paul Roberts who pointed out a simple way of looking at the outbreak using Twitscoop:
The graph suggests 93 posts per second, which is not far from the peak we observed.
Although accurate numbers are hard to extrapolate from the existing data, the total number of malicious posts could have easily exceeded half a million.