Steps to reproduce the issue

1. create multilingual site
2. set english as default language, swedish as secondary
3. create a public menu item in swedish pointing to a registered article in swedish
4. switch to swedish in the frontend, click the menu item link
5. login form is shown, log in with valid username

Expected result

User is logged in and the registered article in Swedish appears.

Actual result

User is logged in, but redirected to the front page and language changed to English.

System information (as much as possible)

Joomla 3.3.6, language filter plugin activated

Additional comments

It seems like the function onUserLogin() in the languagefilter system plugin always uses the site's default language when logging in and not the currently selected language.

Possibly related to [#4079] - #30873 Language Filter Error