Browsers such as Chrome/Firefox has a great feature 'Omnibox'. This great feature save for typed prefix 'stash' first visible address — stash.acme.com/login. Then user type 'stash' and press Enter his always get this page opened. And start to thing, that his is not a logged in, but this is just login form. If you then erase 'login' from URL and press Enter, you get Logged In stash Welcome Page.

The solution is redirect back into Stash root URL, or draw on login page something like 'Hey, you already logged in, mate. Best regards to Omnibox of your browser'.