A tampering vulnerability exists in Microsoft Windows that could allow an authenticated attacker to modify the C:\Users\DEFAULT folder structure. An attacker who successfully exploited this vulnerability could potentially modify files and folders that are synchronized the first time when a user logs in locally to the computer.To exploit this vulnerability, an attacker would need to log on to the affected system and tamper with the DEFAULT folder contents. An attacker can only exploit this vulnerability prior to a user logging on locally to the computer. Users who have logged on before the attacker attempts to exploit this vulnerability would not be affected.The security update addresses the vulnerability by correcting permissions on folders inside the DEFAULT folder structure.