neowin[.]net/reports/windows-10-and-11-users-are-reporting-a-graphical-bug-and-google-chrome-may-be-to-blame/
The symptom is a momentary white rectangle at the top left of your screen. The article talks about it appearing when you first start Windows, but it's occurred for me after ~1.5 hours of use.
The original poster on the Reddit claim has now claimed that they have found a fix for the problem. It's apparently happening due to the GoogleUserPEH folder hosting the RunPlatformExperienceHelperOnUnlock task. A quick search on Google explains that this is a background component associated with Google Chrome that is "designed to manage interactions between the browser and external components, such as extensions, plugins, and update tasks."As such, the fix involves opening Task Scheduler in Windows, navigating to the GoogleUserPEH folder under the Task Scheduler Library tree, selecting the RunPlatformExperienceHelperOnUnlock service, and clicking Disable...
Checking Task Scheduler [Windows Tools] I don't have the task shown in the article's screenshot, so I disabled the two tasks that were there. No idea whether that fixes it or has any other effect, since whatever's happening is random.