Non-Microsoft security flaws cause biggest headache - Most security folks already know this.

The average PC has around 75 programs installed on it, about 39 percent of which are from Microsoft.

This means that the bulk of the patching work is spread across a multitude of small vendors rather than Microsoft alone. In Secunia's view, this represents a major structural issue with patching.

The links below has more details:

http://www.csoonline.com/article/749172/non-microsoft-security-flaws-cause-biggest-headache-says-secunia