Wagtail: Improper permission handling when copying snippets

Wagtail is an open source content management system built on Django. Prior to 7.0.9, 7.3.4, 7.4.3, and 8.0rc2, a CMS user who has add permission for a snippet model but lacks change and view permission for an existing snippet can access the snippet copy view and copy that source object. The copy operation reveals the contents of a snippet that the user is not authorized to view. This issue is fixed in versions 7.0.9, 7.3.4, 7.4.3, and 8.0rc2.