An anonymous reader writes: Core Security issued an advisory disclosing a vulnerability that could affect large numbers of organizations and consumers using Microsoft's Virtual PC virtualization software and leave them open to potential attack. Affected versions of Virtual PC hypervisor contain a vulnerability that may allow attackers to bypass several security mechanisms of the Windows operating system to compromise vulnerable virtualized systems. The issue may also transform a certain type of common software bug into exploitable vulnerabilities. Affected versions of the product include: Microsoft Virtual PC 2007, Virtual PC 2007 SP1, Windows Virtual PC and Microsoft Virtual Server 2005. On Windows 7 the XP Mode feature is affected by the vulnerability.