An updated version, 5.2.3 (and updates to previous versions also), of WordPress has been released which fixes eight security vulnerabilities.
According to WordPress’s changelog the vulnerabilities patched were mainly cross site scripting (XSS) vulnerabilities. More detail on the vulnerabilities and what they mean can be found in this article from Wordfence.
If you are using WordPress for your website you should make sure your WordPress core software is updated. This may have happened automatically, but you should check none the less.