in reply to
The execution of my CGI opens a new navigator window
The execution of your CGI does whatever you tell it to do, it could even destroy your monitor. So until you show some relevant code, there's no way we can tell you the exact situation. It could also be the thing with your browser which you don't let us know either, though it might be irrelevant. Did you consult your browser setting and its default behaviour?
Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!