Using a CMS, companies can easily build sites for themselves and their clients. These systems streamline web design and content publishing, ensuring that both your site and workflow are streamlined.The open source CMS system (Drupal, Joomla, Magento and CMS Made Simple) boost up the market growth and demand. However EU is going to enforce the law on data protection and privacy for all individuals within the European Union. Just do a quick review of the vulnerabiolties found on open source this year (2018). Those vulnerabilities happened are potentially contravention of the data protect law. So company which are going to implement the opensource CMS system, you must be extra care.
Opensources CMS system vulnerability Reference –