Twitter says it's patched a widespread security flaw today that redirected users to third-party sites (sometimes porn) or hit them with pop-up ads. This one was especially heinous, notes Mashable, because it took effect when users simply rolled over an offending link instead of clicking on it. It used a JavaScript function called onMouseOver. Graham Cluley has more at his blog at Sophos.com. See his video in the gallery. (Even Robert Gibbs got bitten by the bug, notes the Hill.)