In the year or so that Firefox 3.0.9 has been out, there have been about 50 official security advisories, 30 rated critical or high severity. Microsoft committed publicly to security improvements several years ago. Windows is neither bug-free nor security hole-free, and probably never will be; that said, its a lot better today than it would have been had Bill Gates not gotten religion about security. If the open source movement is to fulfill its promise, it needs to solve its buggy code problem.”]
Source: https://www.cs.columbia.edu/~smb/blog/2009-04/2009-04-29.html