Guest-post by steveegg
Fortunately, it did not affect, at least directly, those who use third-party Twitter clients like TweetDeck, Seesmic, or the various mobile phone apps. Even more fortunately, Twitter was able to patch this exploit, so now it’s safe to use the web interface again (or so everybody hopes).
If you fell victim to this, I recommend going back through your timeline, searching for any tweet that has “onmouseover” in it, and deleting those tweets. I further recommend running a full anti-virus and anti-spyware scan ASAP.