Amir Sarabadani and Kunal Mehta discovered that the import functionality
of Hyperkitty, the web user interface to access Mailman 3 archives, did
not restrict the visibility of private archives during the import, i.e.
that during the import of a private Mailman 2 archive the archive was
publicly accessible until the import completed.
For the stable distribution (buster), this problem has been fixed in
We recommend that you upgrade your hyperkitty packages.