CellProfiler development is discussed on the cellprofiler-dev mailing list. This is a fairly low-volume mailing list. To subscribe, send mail with "Subscribe" in the Subject field to firstname.lastname@example.org.
How to file new issues
There is a special form for submitting new issues with attachments.
Please attach sufficient information to reproduce the bug. For many bugs, it is appropriate to attach a CellProfiler pipeline and an image.