Upgrade Security Group Provider
If your project organizes user groups (hipposys:group) in (nested) directories (hipposys:groupfolder) under /hippo:configuration/hippo:groups, you may have to adjust the value of the hipposys:dirlevel property on the /hippo:configuration/hippo:security/internal/hipposys:groupprovider node.
If your project had one level of hipposys:groupfolder nodes, and the dirlevel is set to 0 (default), this used to work on CMS 11, but it no longer does on CMS 12. On CMS 12, you should make the value of the dirlevel property equal to the number of (nested) group folder levels in use. You can do so by adding the following definition to your application repository data:
definitions: config: /hippo:configuration/hippo:security/internal/hipposys:groupprovider: hipposys:dirlevels: 1