This bug was fixed in Patch 1.6.69.
My downloaded custom content appears in CAS as clothing for aliens
The filters for my custom content is totally messed up. The clothing is is visible in all categories.
Maxis changed something about the Instance- and Group-IDs which now leads to these issues.
There are none except not to use the custom content at the moment or to live with it.
The next patch is supposed to fix this issue. You will then need to delete the file localthumbcache.package. The file will be recreated and the issue should be fixed.