If you know that the bug you want to report is in the "upstream"
code then please file a bug report in the kaffeine bug tracking system
Kaffeine -> Help -> Report Bug (or on the web at 
http://kaffeine.kde.org/?q=bugs).

If you feel that the bug is one that other Debian users should
know about then you are welcome to file a report in the Debian BTS
as well.  Please keep in mind, however, that managing bug reports
is part of the maintainers' workload and this package currently has
a large number of outstanding reports in the BTS.