The original update KB 4293807 for this security vulnerability was released on August 14, 2018. It exposed certain testing trace flags that were not intended for public release. These trace flags are usually off by default. Therefore, the update has been replaced. If you have previously applied the original update KB 4293807, we recommend that you install KB 4458621 as soon as possible.
How to obtain help and support for this security update
Help for installing updates: Windows Update: FAQ
Security solutions for IT professionals: TechNet Security Support and Troubleshooting
Help for protecting your Windows-based computer from viruses and malware: Microsoft Secure
Local support according to your country: International Support