You might not want to mouseover any links on Twitter until a major bug / security flaw gets resolved. This bug is particularly bad because all you have to do is mouseover a link and potentially third party sites and pop ups can open. The bug is powered by a JavaScript function called onMouseOver and launches a link when the mouse passes over that link. A lot of text link ads work that way in many popular sites. But the fact that this has hit Twitter shows us, once again, that Twitter is definitely susceptible to security attacks.
There is no word yet from Twitter on the status of this bug.
via Mashable