In the space of a given year, untold thousands of vulnerabilities are found in operating systems, applications and plug-ins. But there s also a huge population of security bugs that vendors never fix because they re deemed unexploitable, an assumption that may be turning into a serious mistake for software makers. Microsoft made such a call earlier this year, after researchers at Core Security informed the company that they had found a vulnerability in the Microsoft Virtual PC software. The problem was especially thorny for Microsoft because Virtual PC allows Windows 7 users to run applications designed for older Windows versions in a virtualized environment on Windows 7 machines.
Source: https://threatpost.com/how-assumptions-may-be-making-us-all-less-secure-050310/73913/