Sorry for my English.
Duplicated path url.
Have a domain of the form site.ru/ I press "login"(site.ru/?login). Page opens in a password. If it again click "login" link to the form site.ru/?login?login. Or quickly press the menu items, and the same are obtained here are the url site.ru/home/home/about
I can't really say as we didn't know this was a bug until we re-made WonderCMS with the now host function.
This means we fixed the bug along without knowing it exists. Pretty neat, but unfortunately doesn't answer your question.
If I had put my finger on it, without research, I would say the problem was within the hostname (in index.php) and not defining the root directory of WonderCMS properly in cases where ?login happened.