> What platform hasn't had security issues?
That's reducing things too far. "What car manufacturer hasn't had car crashes?" All cars are equally safe?
There's a vast difference between different languages and CMSs and how likely it is for critical flaws to occur. PHP has a horrible track record and continues to surprise us negatively.
Given the % of traffic of the web it serves and over how long, I actually wonder if you have any proof that PHP actual track record in on the bad side because I think it will probably be on the better side actually, same for Wordpress specifically.