Windows has been key-logging your computer since Windows 7 or Windows 8, and leaves the file completely unsecure. That's what this TechSpot article is suggesting after a Digital Forensics and Incident Response expert found a "TextHarvester" file that is created by the Windows 10 handwriting recognition tool, which stores every text file it can find.

Read more on TechSpot: https://www.techspot.com/news/76575-windows-recording-every-keystroke-devices-handwriting-recognition-enabled.html

Your file can be found: C:\Users%user%\AppData\Local\Microsoft\InputPersonalization\TextHarvester