French information security company VUPEN has recently disclosed that it held onto a serious Internet Explorer (IE) vulnerability for at least three years before revealing it at the Pwn2Own hacker competition held in March this year. The critical zero-day vulnerability affected versions 8, 9, 10 and 11 of Internet Explorer browser that allowed attackers to remotely bypass the IE Protected Mode sandbox. Sandbox is security mechanism used to run an application in a restricted environment. If an attacker is able to exploit the browser in a way that lets him run arbitrary code on the machine, the sandbox would help prevent this code from causing damage to the system.
Source: https://thehackernews.com/2014/07/exploit-selling-firm-kept-internet.html