Twitter enthusiasts were in for a surprise today when they sat down for their early morning “tweet” and a cup of coffee. The short-messaging service was hacked as mysterious tweets of blocked-out text propagated themselves and caused pop-up windows to open unexpectedly. According to Mashable, the bug redirects users to third-party websites without their consent.

The hack had been particularly nefarious because the tweets activated without being clicked on. Web surfers needed only move their mouse cursors over them to become at risk. That’s because the pop-ups contained malicious code that could take control over poorly protected computers. In fact, Fox News reported that that some of the redirects sent users to explicit websites. A source told Fox News that "tens of thousands if not hundreds of thousands of messages" had been posted to Twitter as a result of the hack.

But not everyone was affected by the attack. While visitors to Twitter.com were impacted, third-party programs used to send and read tweets were left untouched.

According to Twitter's Trust and Safety team leader Del Harvey, the Twitter hack has been identified and is now fixed. “The XSS attack should now be fully patched and no longer exploitable," Harvey said from here Twitter account @delbius. “Thanks, those reporting it.”

This isn’t the first time Twitter has been hacked. In May, a Twitter security glitch allowed any Twitter user to force another to subscribe to their ‘tweets’ without the ‘follower’ giving permission. As a result, thousands of celebrities, including Justin Bieber, P. Diddy and Ashton Kutcher, found themselves following complete strangers. Tweeted reality TV star Kim Kardashian: “Someone hacked my account and direct messaged me! They have added over 200 new people! Ughhhh.”

As for a culprit, the Toronto Sun is reporting that today’s malicious attack originated from Twitter user @Matsta, and that the website for Matsta.org directs users to a Rick Astley music video. Misdirecting Internet users to this video has for years been an online practical joke known as “Rick-Rolling.” The Twitter account for @Matsta has been suspended since this morning’s Twitter attack.

Despite today’s hack job, Twitter can probably rest assured that when it comes to using the popular messaging service, enthusiasts are still singing “Never gonna give you up.”