The second instance of Windows PCs updating themselves without user permission might be a user problem, not another “stealth update” like the one in September. The reports have only cropped up on the AeroXperience website, while Microsoft’s Automatic Updates support group has remained silent about these issues. Microsoft’s update program managers investigated and found that none of the patches changed any settings. User action is required for all five of the scenarios described as possible causes for the changes.
Since the problem only affects Windows Vista, I can’t say if it was a Microsoft change or a user thing.