This might need to be reclassified as something other than a defect.

If you are running a presentation, and the presentation calls for another
document to be opened (for example, there is a hyperlink), the application that
handles that document (for example, Firefox or IE) opens BEHIND the
presentation, so that the document is not viewable unless the presentation is
closed.  In Windows, the behavior is different, the application opens in front
of the presentation, so that it is viewable without closing the presentation. 
Also, both Keynote and PowerPoint open the application in front of the
presentation even on this system where Impress does not.

It is simple to recreate:  Create a presentation, add a hyperlink to one slide,
run the presentation, click on the hyperlink.  The application will open behind
the presentation.