Instances can go down, disappear or be unresponsive due to many reasons.
Go to your account settings now and export your account settings!
This file contains your subscriptions, follows, profile settings etc. It’s very easy to start over on a new instance when you have your export file.
Back it up, export it, save it, repeat occasionally.
No websites should be able to access anything on your hard drive arbitrarily.
Websites can ask the browser to store something in cookies, or local db storage; it can even say “here’s a file for download”. But it cannot just decide to place a download somewhere in your filesystem.
The browser itself is accessing your filesystem to read and write cookies, cache, etc. and the website has (rightfully so) zero control over that, other than asking permission and offering up a link to something the browser may to may not decide what to do with.
Didn’t claim arbitrary access, just writing to hard drive. But I see, so the browser is the mediating layer