Wordpress is used for more than 25% of internet sites. That also means that is the CMS most hacked :)
Fortunately the WP and its community is working hard to fix the problems asap and make new release.
The major problem is that people doesn't update the cms. I really recommend the auto-updated and a good management of all plugins versions. If you are a delveoper and you are taking care of several wp sites, there are many plugin that can help you to manage the WP and plugins versions for a large number of sites.
Fortunately the WP and its community is working hard to fix the problems asap and make new release.
The major problem is that people doesn't update the cms. I really recommend the auto-updated and a good management of all plugins versions. If you are a delveoper and you are taking care of several wp sites, there are many plugin that can help you to manage the WP and plugins versions for a large number of sites.