This is just a test for the OPFS feature in Webbrowsers. It is a kind of editor for the poor. You can use it to place text files on your local filesystem using opfs.
Firefox places the files in this path:
~/.mozilla/firefox/<yourprofile>/storage/default/<domain>/fs/
A subdirectory is created there, which contains a file composed of 52 digits (letters and numbers).
It's just a Hash of the original Filname.
This file contains the original content as it was entered via the webapplication.
However, this file cannot be made executable by the creator.
A sqlight database is also created in this path, which contains the metadata.
In Firefox this feature was introduced with version 111.
You can Test it here: