For the second time in three days, Twitter finds itself as the target of a malicious attack. On Saturday, a phishing scam was running through direct messages. Today, we’ve received word that certain well-known Twitter users have found tweets injected into their timeline. Victims include President-Elect Obama, Bill O’Reilly of Fox News, Rick Sanchez of CNN, and Britney Spears.

This is another warning message to the rest of us. Even though you probably haven’t been compromised, you need to be watching your own stream for strange tweets. If you’re afraid you’re going to be a victim, change your password. If you see something in there that you didn’t put there, change your password. Here are some tips to creating a safe password.

If you see anything fishy, send a tip to tips [at] microblink [dot] com.

Update: Twitter’s Status blog claims they’ve found the cause and blocked it and are working to restore the compromised accounts.

Update 2: Twitter’s official statement says that 33 accounts were compromised. They’re also saying that it was a separate incident from the weekend’s phishing scam.