if you are a customer or partner, you can report bugs via the respective portals on the Qlik.com site.
AFAIK, there is no direct way to report a bug if you are not a partner, customer or Qlik employee.
Are you a customer or partner?
Then I would still recommend using the respective portals.
From my experience, bugs posted to the community (including the QlikBug space) will rarely lead to a close bug related collaboration with Qlik employees. AFAIR, the QlikBug space was only created because there was a need for QlikView users to exchange about found bugs, having no publicly available defect tracker at hand.
Maybe rbecher as one of the place admins can comment on his experience.
Qlik Support Portal is the right place for clients and partners to log a case:
The QlikBug Group I've created with my colleague is a place to share what you might think is an bug, issue or wrong behavior. And probably other members can help or already know more about a submitted case, or can provide a workaround. But, it's not place to get a bug fixed..