We use GitHub issues to track bugs. Issues are logged on individual project repositories, but you can view all issues collected together here.
If you'd like to report a new bug, first check that the issue hasn't already been filed by searching through the board above. If this is a new bug, you can report it by opening a new issue on the appropriate repository. If you're not sure which repository is most appropriate for the issue, you can email us instead at firstname.lastname@example.org.
Ensure that your report clearly indicates both the behaviour that you expect to see, and the behaviour that you are actually seeing. Ideally, please also include a list of steps to reproduce the error you are seeing. The project repository should be pre-configured with appropriate issue templates, so please try to follow those directions!