The Numbers Speak for Themselves
The top 4 pieces of most commonly used vulnerable 3rd party software in 2012 / 2013 / 2014 are:
1. Oracle Java Runtime environment
2. Adobe Acrobat Reader
3. Adobe Flash Player / Plugin
4. Apple Quicktime
Of these 4, Adobe Flash Player accounts for 314 registered vulnerabilities alone in 2015. That comes to 26 vulnerabilities PER MONTH! The next piece of software on the list is Acrobat Reader with 130 vulnerabilities or 10,8 per month, still quite high, but not as extreme.
All this data is more than scary. Intelligence shows that usage of Java, Acrobat Reader and Adobe Flash Player is very common on business computers and has been for a while. The good news is that Flash usage has dropped significantly, mainly because HTML 5 replaced the need for having it installed, but also because Flash was a preferred attack vector in 2015. Meanwhile, the widespread usage of software is most likely linked to the fact that we consume more and more data on the computer, and that we access a broader variety of software to do so.