If a bug in a software is not specific of Ubuntu, but can also affect other operating systems as well, it needs to be reported to the upstream developers.
For that, if the upstream project isn't already listed in the panel, click on the "also affects project" button to add it.
In some cases Launchpad will also ask you to provide a link to an upstream bug report. In that situation:
Check if a link to an upstream report is already posted into the Launchpad report.
Figure out where the upstream bug tracker is.
Add the upstream project without providing a link.
Set the bug status to "incomplete".
Ask the user to report the bug to the upstream bug tracker too, to paste the upstream report in Launchpad, and to set the bug status back to "confirmed".