How to reproduce:
- Wander aimlessly into some meta site (either, logged on some other site or not logged at all)
- Try to upvote/downvote/do something that requires you to be logged in (this will trigger the login or create an account)
- Click any login option
- ...
- ....
What happens?
You get a 404 not found error.
What this silly user thinks should happen?
Either, allow me to login or do not show me the box to login in the first place.
Impact?
All per-site metas.