WordPress 4.9.1 Security and Maintenance Update
WordPress have released a security update for all versions since WordPress 3.7 which fixes four discovered security issues which could potentially be exploited as part of a multi-vector attack.
This release also includes 11 other maintenance fixes to the 4.9 release series.
You are recommended to update your WordPress version immediately.
Remember to always take a full backup of your files and database before running updates!