On Wednesday and Thursday, five contestants -- four teams and one independent researcher -- demonstrated three successful remote code execution attacks against Safari on OS X, two against Microsoft Edge on Windows, four against Adobe Flash on Windows and one partially successful attack against Google Chrome on Windows. Firefox was not a target in this year's contest.
It's not really surprising that experienced security researchers found vulnerabilities in all browsers that allowed them to execute rogue code on the targeted systems. This happens almost every year at Pwn2Own.
However, the complexity of the attacks stood out, some involving exploit chains that took advantage of up to four vulnerabilities. This is a testament to the security improvements made by browser and OS vendors in recent years.
It's no longer enough to find a single browser flaw in order to take complete control of a computer when it visits a specially crafted website. That flaw needs to be combined with others to bypass sandbox protection mechanisms or to execute code with the highest possible privileges -- those of the "system" account on Windows or the "root" account on OS X.
This year, the contest offered a $20,000 bonus for privilege escalations to "system" or "root" and every single successful attack took that bonus, mostly by leveraging vulnerabilities in the OS kernels.
Out of the 21 total vulnerabilities, six were in browsers and six were in the OS kernels. The rest were in Flash Player or OS components and processes.
The Google Chrome vulnerability turned out to be a duplicate of a flaw that had previously been reported to Google by an independent researcher before Pwn2Own. Because of this, the Google Chrome attack was ruled only a partial success.
"It’s a truism in security that when you harden one area, attackers and researchers will move their attention to another one," the contest organizers from security firm Trend Micro, said in a blog post. "Based on Pwn2Own 2016, it appears that’s happening with a shift to focus on the kernel."
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