Microsoft is testing a suite of Office progressive web apps in Windows 10 without asking permission from the user. Progressive web apps are designed to be delivered via the web without installing executables on the computer. Microsoft has been forcibly installing Word, Excel, PowerPoint, and Outlooks PWAs into Microsoft Edge and registering them with Windows 10. This appears to be an A/B test, with only some users receiving the new PWAs. Uninstalled applications can be found through the Programs and Features settings page.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-is-forcibly-installing-office-pwas-in-windows-10/