When user switches between "Log in" and "Sign up", the
returnurl parameter get lost.
Here is how to reproduce it:
- Open a private tab or log out.
- Go to a question.
- Try to upvote something. At "Thanks for feedback!" pop-up, click on one of "Sign up using ..." buttons.
- Realise that you clicked on "Sign up" button instead of "Log in", so switch tabs.
- Log in but, oops, where is the question?