Will your application install as an extension? In that case, you can use XPCOM: https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsICookieManager

If your application is meant to run as an applet in a web page, your application probably does not have permission to access cookies, other than the ones set by the same host.

Thank you. My application is meant to run as an applet in a web page. Still I hope it's possible to access firefox cookies from an applet somehow.

For help on this, you could try the Extension Development forum at MozillaZine: http://forums.mozillazine.org/viewforum.php?f=19

Thank you very much! I'll try it.