Many websites are now built with some sort of content management system attached to it to allow the owners access to go into the backend of a website and make changes. The types of changes you can make to the site through the CMS system often include adding or editing content, adding or editing products or services that can be purchased, creating new users, extracting data from a database such as a brochure request form and making certain layout changes to the website.
If the content management system is hacked you can end up with all sorts of problems and find yourself having little control over what is being added or removed from the site. Your website content could be changed to include harmful links, misrepresentations or even deleted entirely. If accessed it could also mean that sensitive data such as customer email address, phone numbers and postal addresses are accessed and then sold on.
It is vital to ensure that you content management system is secure and has the latest updated version installed. If you use an off the shelf content management system such as WordPress, updates are very easy to do.