Quoting:Using the proprietary OOXML document format, i.e. docx, pptx and xlsx, makes you more vulnerable to phishing and other attacks. Earlier this month, the Japanese anti-virus company Trend Micro published a blog post describing how the attack group "Operation Pawn Storm" uses spear-phishing mail messages with malicious Office documents to target the military, governments, defense industries and the media.

Four years ago, Thomas Caspers and Oliver Zendel from the German Federal Office for Information Security (BSI) already presented research results stating that most spear-phishing attacks targeting specific persons or a small group of victims are using "launch actions" in Office and PDF documents to have their malicious code executed.

All in all, the researchers concluded, using the OpenDocument standard — the default format used by the open source package OpenOffice/LibreOffice — improves your IT security.