UPDATE: For our latest coverage of this issue, please see How StalkDaily Opened a Gaping Hole in Twitter
Twitter users beware: a site called StalkDaily (don't visit it, please) has been infecting Twitter profiles today with a spam worm that forces accounts to send spam tweets towards the StalkDaily website.
If you're not yet affected, do not click any links to the StalkDaily site. And if you are an unfortunate victim, it's wise to:
1. Go to your browser settings and clear your cache and browser cookies
2. Change your Twitter password and remove the offending Tweets.
As with similar attacks, it's likely that Twitter will put a stop to StalkDaily very shortly, possibly by blocking links to the site. For now, the best advice is to avoid the site and follow the above instructions.
StalkDaily Denies Involvement
Interestingly, we visited StalkDaily today in a secure browser environment, and found a denial posted by the site owner. Was he or she a victim too, as the site claims?
Update: More Serious Than First Thought
It now appears that unlike previous attacks, where clicking a link would cause your account to get affected, the code for infecting Twitter accounts resides on Twitter pages themselves - simply visiting a Twitter page affected could spread the attack. The advice remains the same but with these additional steps:
3. If anything on your Twitter profile (particularly the site in the "website" field) has been changed, switch it back
4. Do not visit Twitter profiles on the web until the issue is patched.
5. Follow the Mashable comments (below) for further updates.