The short answer is "Yes".
VON trusts the SaaS provider that hosts the downloads, a leading CRM/Helpdesk vendor.
Reply from ZenDesk:
Craig Lima (Zendesk Support)
Apr 26, 14:44 PDT
Hi Ted, apologies on the lateness of reply (we have been extremely busy).
As for attachments, currently all attachments are stored in S3 and encrypted at rest via AES 256.
Zendesk has traditionally exposed attachments in tickets as a link to the attachment in said buckets. You may gate attachments by requiring authentication to your instance in order to download them if you so desire. You can also delete attachments either via the API, or via the UI when using the Ticket Redaction App.
We are now moving to actually attaching attachments directly to messages in lieie of only surfacing a download link. The encryption and gating controls are still in place.
I hope that helped Ted!
Craig A Lima