Microsoft is warning Windows 10 users not to install the Oct. 15 update because of a glitch that causes Defender Advanced Threat Protection to break.

Despite containing only non-security fixes, update KB4520062 has been found to cause serious security issues related to Windows Defender ATP. A bug included in the patch is reportedly forcing Defender's security tools to stop and keeping it from sending crucial report data.

The software developer said the problem seems to affect PCs running on Windows 10 version 1809, as well as those using Windows Server 2019.

The good news is that since KB4520062 is only the second cumulative update for the month of October, Windows 10 users are not required to install it.

Defender ATP Security Issues

Windows Defender Advanced Threat Protection is mostly used to help protect enterprise networks from unauthorized breaches. As its name implies, the system is capable of addressing advanced threats whether through prevention, detection, investigation, and response.

Businesses often rely on Defender ATP's security tools such as its antivirus, endpoint device monitoring, and threat intelligence. Microsoft has built these features directly into Windows 10 Enterprise offering.

While organizations don't necessarily have to install the Windows 10 1809 Oct. 15 update, those who may have already done so would likely experience problems with their Defender ATP program.

Microsoft said sufferers might see their security software suddenly stop and fail to send any reporting data. They might also receive an error message (0xc0000409) in the Event Viewer on their MsSense.exe program.

Microsoft Working On A Solution

As of the moment, Microsoft is still looking into the KB4520062 update bug to come up with a fix. The company estimates that it will be able to release a solution for the issue with the upcoming Windows 10 November patch.

However, there's still no guarantee that the fix will be available by the time the November Patch Tuesday update becomes live. The event usually occurs on Nov. 12.

"At this time, we suggest that devices in an affected environment do not install KB4520062," Microsoft said. "We are working on a resolution and estimate a solution will be available in mid-November."

This is not the only ongoing Windows 10 issue people are still waiting for Microsoft to fix. Some users have been getting a critical error related to the Start menu on their PCs. The problem allegedly started right after the release of the October Patch Tuesday update.

Microsoft promised users that it will release a resolution for the Start menu error, but it has yet to do so. The software developer said it should be available by late October.