One of the biggest downsides to having the power and flexibility of a WordPress website with much benefits, is security! More specifically exploits and breaches with outdated plugins. Below is a great article for the proof that despite developers best attempts to create the most rock solid platform out there. Exploits happened and will continue to happen, and the only remedy is take security seriously by protecting your site, or at the very least keeping your site up to date!
A History of WordPress Security Exploits and What They Mean For Your Site