Microsoft has said it is aware of targeted attacks and is investigating a vulnerability that could let hackers gain user rights to affected computers.
The firm says hackers could exploit a vulnerability in its operating system by requesting users to preview or open a specially crafted email or web content.
The issue affects Windows Vista, Windows Server 2008, Microsoft Office 2003 - 2010, and Microsoft Lync.
Microsoft is advising customers to apply workarounds while the firm addresses the issue. Visit Microsoft’s Security Response Center for more information on workarounds.