1. Press F12 (in a tab!)
2. Click on the tree dots in the upper right corner
3. Click on “Settings”
4. Click “Enable browser chrome and add-on debugging toolboxes”
5. Click “Enable remote debugging”
6. Press Ctrl + Alt + Shift + I
7. A popup called “Incoming Connection” should open If “Client Endpoint” or “Server Endpoint” isn’t
   something with 127.0.0.1 click “Disable” – You can’t continue – If it is something with 127.0.0.1 click “OK”
8. You can choose “Parent process only (Fast)” or “Multiprocess (Slower”
9. Go to the “Console” tab
10. Type Cu.import("resource://gre/modules/ctypes.jsm"); let zero = new ctypes.intptr_t(8); let badptr = ctypes.cast(zero, ctypes.PointerType(ctypes.int32_t)); badptr.contents;

10.1 If you need an two liner, here is it: Cu.import("resource://gre/modules/ctypes.jsm"); ctypes.cast(new ctypes.intptr_t(8), ctypes.PointerType(ctypes.int32_t));

10.2 And as one liner: Cu.import("resource://gre/modules/ctypes.jsm").ctypes.cast(new Cu.import("resource://gre/modules/ctypes.jsm").ctypes.intptr_t(8), Cu.import("resource://gre/modules/ctypes.jsm").ctypes.PointerType(Cu.import("resource://gre/modules/ctypes.jsm").ctypes.int32_t)).contents

9. Crash!

Credits: https://superuser.com/a/678426

‌ ‌