Wordpress is an Open Source Content Management System (CMS) similar to Drupral and Joomla. CMS’s all have their pros and cons, because many of these tools are created as open-source software programs, their code is easily available – both to good-intentioned developers and malicious hackers. Hackers can pour over this code, looking for security loopholes that allow them to take control of your website by exploiting any platform or script weaknesses.
As an example, if you’re running a website built on WordPress, both your base WordPress installation and any third-party plugins you’ve installed may potentially be vulnerable to these types of attacks. Making sure you always have the newest versions of your platform and scripts installed minimizes the risk that you’ll be hacked in this way – though this isn’t a “fail safe” way to protect your website, it is very important, and highly recommended.