Previously, websites could only access files and services of your computer through the use of Java or ActiveX plugins. However, thanks to the new Native File System API update included in Chrome 78, websites can simply open a file picker dialog, allowing them to open, upload and make changes to files on our computers without the need for plugins. Thankfully, Google thought of many controls to implement prior to implementing this update. These include: Limiting access to files by requiring permission to be granted by an admin account for every file to be opened, requiring permission for every change to be made, and an indicator in the address bar that shows if you have given a site file permissions.
Source: https://tech.slashdot.org/story/19/11/02/2323246/chrome-tries-apis-that-allow-changing-a-users-files-receiving-sms-verification-texts