Wagtail: Improper permission handling when copying snippets

Impact A CMS user with "add" permission over a snippet model, but not "change" or "view" permission, could copy an existing snippet that they do not have access to, allowing them to view its contents. Patches Patched versions have been released as Wagtail 7.0.9, 7.3.4, 7.4.3 and 8.0rc2. Workaroun...