Google has pledged cash prizes totaling $1 million to people who successfully hack its Chrome browser at next week's CanSecWest security conference.

Google will reward winning contestants with prizes of $60,000, $40,000, and $20,000 depending on the severity of the exploits they demonstrate on Windows 7 machines running the browser. Members of the company's security team announced the Pwnium contest on their blog on Monday. There is no splitting of winnings, and prizes will be awarded on a first-come-first-served basis until the $1 million threshold is reached.

Now in its sixth year, the Pwn2Own contest at the same CanSecWest conference awards valuable prizes to those who remotely commandeer computers by exploiting vulnerabilities in fully patched browsers and other Internet software. At last year's competition, Internet Explorer and Safari were both toppled but no one even attempted an exploit against Chrome (despite Google offering an additional $20,000 beyond the $15,000 provided by contest organizer Tipping Point).

Chrome is currently the only browser eligible for Pwn2Own never to be brought down. One reason repeatedly cited by contestants for its lack of attention is the difficulty of bypassing Google's security sandbox.

"While we’re proud of Chrome’s leading track record in past competitions, the fact is that not receiving exploits means that it’s harder to learn and improve," wrote Chris Evans and Justin Schuh, members of the Google Chrome security team. "To maximize our chances of receiving exploits this year, we’ve upped the ante. We will directly sponsor up to $1 million worth of rewards."

In the same blog post, the researchers said Google was withdrawing as a sponsor of the Pwn2Own contest after discovering rule changes allowing hackers to collect prizes without always revealing the full details of the vulnerabilities to browser makers.

"Specifically, they do not have to reveal the sandbox escape component of their exploit," a Google spokeswoman wrote in an email to Ars. "Sandbox escapes are very dangerous bugs so it is not in the best interests of user safety to have these kept secret. The whitehat community needs to fix them and study them. Our ultimate goal here is to make the web safer."

In a tweet, Aaron Portnoy, one of the Pwn2Own organizers, took issue with Google's characterization that the rules had changed and said that the contest has never required the disclosure of sandbox escapes.

Ars will have full coverage of Pwn2Own, which commences on Wednesday, March 7.

Updated to make clear Pwnium is a contest that's separate from Pwn2Own and to add comment from Portnoy.