Windows Update has the ability to update itself as controlled by Microsoft's Update Servers. This update offers no control to the administrator of the machine, and forces the machine to install the update if it is connected to the Microsoft Servers.
One thing that makes this development alarming is that the process reveals a backdoor which could allow malicious parties to alter the service; if the update process were to be reverse engineered. This is a substantial security hazard to the OS, because it means that the OS has the ability to be directly altered without administrator control on a system which was previously secure.
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