Private groups shown in Contribution Receipt

Here's how to reproduce.

1. add "group(s)" as a field in a profile used on a contribution page
2. note that only public groups appear on the profile as webpage (correctly)
3. find a contact and add that contact to several groups, both public and private (e.g. 2 private groups and 1 public group)
4. as that contact, make a contribution on the page from step #1
5. in the receipt note that ALL the groups are shown in the field within the profile, not just public groups (incorrectly)