The vulnerability can be exploited through an attack scenario known as cross-domain theft, and researcher Chris Evans originally brought the problem to light in a blog post in December. At the time, all of the major browsers were vulnerable to the attack, but since then, Firefox, Chrome, Safari and Opera all have implemented a simple defense mechanism. The upshot of this is that if a victim has visited a given Web site, authenticated himself to the site, and then visits a site controlled by an attacker, the attacker would have the ability to hijack the user's session and extract supposedly confidential data. This attack works on the latest, fully patched release of IE8, Microsoft's flagship browser."
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