Google says its bug bounty program, which awards hefty cash rewards for privately reported security vulnerabilities in its Chrome browser and online services, has been such a success that the company will expand it to include Chrome OS.

To date, Google has shelled out $729,000 under the program, which was initiated two years ago for its Chrome browser and 15 months ago for YouTube, Blogger, and its other Web services. Over the course of the latter program, Google received 1,100 legitimate reports from more than 200 individuals, Adam Mein, technical program manager on Google's security team, blogged. Of the 730 bugs that qualified for a reward, about half were contained in software developed by one of 50 or so companies Google has acquired. In all, Google has paid $429,000 under that program.

The remaining $300,000 was paid under the older bounty program for the Chrome browser, according to a separate post published on Google's Chromium blog. Reported flaws have covered the gamut of browser components, including Windows kernel and Mac OS X graphics libraries, code for the underlying Chromium and WebKit browser libraries, and open-source libraries such as libxml and ffmpeg. The post said "dozens of researchers" had submitted reports.

Google said it will now open up the program to those reporting "high-severity Chromium OS security bugs" that are present when the system's developer mode is turned off. Eligible issues include renderer sandbox escapes using Linux kernel flaws, memory corruptions or cross-origin issues inside the Pepper Flash plugin, and violations of the verified boot path will all qualify.

Started in early 2010, the bug bounty program for the Chrome browser was one of the first times a software developer had agreed to pay cash rewards in return for vulnerability reports. (Mozilla and DNS software developer Daniel J. Bernstein both preceded Google.) In July, Facebook initiated its own rewards program. So far, Microsoft, Apple and Oracle have declined to pay rewards, despite the considerable—and free—help they receive from some of the world's most talented security researchers.