Quote
JavaScript and Timing Attacks Used to Steal Browser Data
Security researchers have been warning about the weaknesses and issues with JavaScript and iframes for years now, but the problem goes far deeper than even many of them thought. A researcher in the U.K. has developed a new technique that uses a combination of JavaScript-based timing attacks and other tactics to read any information he wants from a targeted user's browser and sites the victim is logged into. The attack works on all of the major browsers and researchers say there's no simple fix to prevent it.
http://threatpost.com/javascript-and-timing-attacks-used-to-steal-browser-data/101559