QuickLook in Apple Mac OS X 10.6 before 10.6.8 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted Microsoft Office document.
http://support.apple.com/kb/HT4999
http://support.apple.com/kb/HT4723
http://lists.apple.com/archives/security-announce/2011//Jun/msg00000.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html