Twitter: All Safe after Mysterious Hack

Twitter repaired a hack Tuesday that caused mischief to spread on through its short-messaging service, as mysterious "tweets" of blocked out text propagated themselves and caused popup windows to open for thousands of users.

The hack that spread was extra nefarious because the tweets activated without being clicked on — it was enough for web surfers to move their mouse cursors over them.

Twitter said it identified the exploit and successfully patched it.

The hack only appeared to affect visitors to Twitter.com. Various third-party programs used to send and read tweets appeared to be unaffected.

The popups could have contained malicious code that could have taken over poorly protected computers.