Windows 10's October update has been relatively problem-free so far, but it's a subsequent patch which is causing problems for some users.
The KB456781 is a cumulative update for devices running version 2004 (May 2020) or 20H2 (October 2020). It's designed to improve security across Microsoft Office, basic operations and input devices like mice and keyboards, but many people have had issues installing it.
As Windows Latest reports, many people were unable to update their device altogether. Messages such as "Some update files are missing or have problems. We'll try to download the update again later" are accompanied by 0x8007000d or 0x800f0831 error codes. Some users also report that the installation of the KB456781 patch would seemingly take a long time before displaying a 0x80070308 error, while others saw it count up to 100% and then abort.
For the small percentage of users who managed to successfully install the update, the issues didn't end there. Other people have said that KB456781 lead to the mouse pointer blinking or Edge browser launching slowly.
At the time of writing, Microsoft is yet to officially acknowledge the issues. However, it's worth saying that these issues will only affect a small number of users, and more severe problems such as system crashes or blue screens are highly unlikely. The most common issue, not being able to install it at all, won't have any lasting impacts on your device and your device won't be at risk without it.
In Microsoft's official guide to the patch, the company confirmed there will be no preview releases for December 2020. This temporary suspension coincides with the upcoming Christmas and New Year season.
This patch comes between the release of two Windows 10 feature updates. The October update continues to be rolled out after following official release at the end of last month, while we're already looking ahead to a potential 21H1 update.