Imagine you have Permission to post as [email protected] as an object that is locked in a safe deposit box, the key is JWT token.

The key, by how it works, can be obtained by (1) knowing [email protected]'s password (+2FA token if configured) (2) have a copy of the token (3) somehow cheat lemmy.world's authentication scheme (by somehow skipping authentication or acquiring magic tool to generate random token .... etc).

What happened today is scenario (2), by a single line of JavaScript planted by hacker, and if you have access to my unlocked desktop computer, you can see and copy the key by using F12 (developer tool).

Scenario (2) can be mitigated by tying the sending computer IP to JWT token, but as far as I can tell lemmy.world doesn't have the option, and most of people get random new IP address every now and then because how Internet currently operates, so this feature can be very annoying.

now introduce Permission to post PGP signed message as [email protected] as an object that is locked in a safe deposit box, this deposit box has two key slot (like a bank deposit box), JWT token and PGP private key.

This PGP private key doesn't have to sit in your browser, it can be on a burner phone which it's only purpose is a APP for signing message, it can be on a USB thumb drive that is stored in your parent's basement, or usb thumb drive that sits in bank deposit box which requires a bank employee to authenticate your ID to access.........

First of all, it's still possible, as you said. Second, we must always take humans into consideration. Let me explain.

Most people don't know what PGP is, thus you can sign your posts with any crap and most won't care.

Out of those who know what PGP is and how to use it, most won't be checking the posts as they will auto-assume that if it's signed - it's ok.

There will be a small minority of those who care, but they can be silenced easily through social engineering.

It is possible to integrate server side signature checks, but then again you're vulnerable when someone gains unrestricted access to your account.

The correct solution requires multiple features to be implemented.

1. Lemmy web UI should move to an industry standard framework, which disables XSS and other attack vectors by default. For example, Angular.
2. Official admin announcement, as well as important admin tasks, should require 2FA on each action. Like it's done on GitHub, for example.
3. Cookies should not contain JWT tokens, they should only cotain session id for read only purposes. JWT token should be moved to sessionStorage instead. It's a lot more secure by design than cookies. You can still exploit it, but it's noticeably harder.