In brief: Microsoft's latest cumulative update, KB4482887 (OS Build 17763.348), was supposed to bring many mainstream, quality of life improvements to Windows 10, including limited support on certain devices for the new retpoline patch that helps with Spectre mitigation performance. Instead, users are reporting performance issues with games and with mice. Microsoft has acknowledged this and is working on a solution.
The most recent Windows 10 cumulative update, version 1809 KB4482887, is reportedly tanking performance in certain titles and causing adverse mouse effects. So, if following the February update rollout, you've noticed your mouse or games are misbehaving, it's likely nothing to do with your system but the operating system.
In the release notes, Microsoft acknowledges the issue as known and notes users may see graphics and mouse performance degradation in games like Destiny 2. However, while the impact appears to be game specific rather than global, Destiny 2 is not the only title suffering. According to users on reddit, older games like Call of Duty 4 and Call of Duty: Modern Warfare 2 are also pained by the update.
Supposedly, other affected titles include the newly popular Apex Legends and Sea of Thieves.
Ironically, KB4482887 also enabled the "retpoline" Spectre mitigation on certain devices. Although that's unlikely the culprit and has to be enabled manually. KB4482887 also comes with many other quality of life improvements for Windows 10, and since no major non-gaming issues have been reported, users that do not play games may have nothing to worry about.
Microsoft has said it's working on a fix to be rolled out in a future update, and its official guidance is to uninstall KB4482887 and wait for further resolution.