Note: We recommend you install the latest updates to avail all latest fixes.
You are getting the error message "Unknown Error. Code - 15613", when you try to install the following Windows updates to your endpoints.
Because of an issue that affects some versions of antivirus software, the above updates cannot be applied to computers on which antivirus is installed and the following registry key is not set.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\QualityCompat\cadca5fe-87d3-4b96-b7fb-a231484277cc
Microsoft resolved this issue in the latest monthly security and quality updates. So we recommend you to deploy the latest updates.
For Windows 7, Windows 8.1, Windows Server 2008 R2, Windows Server 2012

For Windows 10 and Windows Server 2016

Applies to: Meltdown updates, Spectre updates, Meltdown and Spectre security updates, Microsoft security updates, antivirus compatibility issue
Keywords: Meltdown and Spectre updates, Meltdown updates, Spectre updates, Antivirus compatibility issue, Microsoft security updates