Google's Chrome browser on Friday fell to a zero-day attack that pierced its vaunted security sandbox, the third such attack in as many days at a contest designed to test its resistance to real-world threats.

A teenage hacker who identified himself only as PinkiePie said he spent the past week and half working on the attack. It combined three previously unknown vulnerabilities to gain full system access to a Dell Inspiron laptop that ran a fully patched version of Chrome on top of the most up-to-date version of Windows 7. He spent the past three days holed up in hotel rooms and conference areas refining the attack so it would break out of the sandbox, which was designed to prevent code-execution attacks like his, even when security bugs are identified.