Steps to reproduce
- Open example.com/login.
- Open browser devtools.
- Get value for
- Open example.com/login in the incognito tab.
- In the incognito tab, change cookie value to the one, obtained in step 3.
- In the normal tab (the one from steps 1-3) log in as any user.
- Refresh page in the incognito tab.
You are now logged in the incognito tab as user from step 6 as well.