A zero-day vulnerability has been exploited in the wild on Windows 7 systems. Google recommends users of Windows 7 to give it up and move to Microsoft s latest operating system. The vulnerability is a NULL pointer dereference in win32k!MNGetp ItemFromIndex when NtUserMNDragOver() system call is called under specific circumstances. Google believes that this is the only version of the OS where it works because the exploit mitigations Microsoft introduced in newer versions of OS, Windows 10 in particular, would prevent it.
Source: https://www.bleepingcomputer.com/news/security/google-advises-upgrade-to-windows-10-to-fix-windows-7-zero-day-bug/