Microsoft is investigating complaints from Windows users that patches have been installed without their consent as a result of the Automatic Update (AU) application being turned on without their knowledge.
Complaints have been made following the company releasing a batch of security patches last Tuesday.
Nate Clinton, program manager for Microsoft Update, said on the Microsoft Update blog, "We have been hearing some questions recently regarding Tuesday's update release changing automatic updating settings.
"We have received some logs from customers, and have so far been able to determine that their Automatic Update settings were not changed by any changes to the AU client itself and also not changed by any updates installed by AU."
Clinton said, "We are still looking into this to see if another application is making this change during setup with user consent, or if this issue is related to something else."
There is a suggestion that any problem may be caused by the Microsoft Office suite or Redmond's Windows OneCare security protection service.
Many users do not want automatic updates as they can be received at inconvenient times when other applications are being used, and can slow wireless connections.
Some updates can also be inappropriate and can change settings to other programs, so a number of users like to select which patches are installed.