Hi all,
After our Pro Cloud instance auto-upgraded to **v1.61.3**, basic **Row and column security** (Filter by a column = user attribute) on a MongoDB collection started dropping all **unfolded nested fields** for the sandboxed group. It was working fine the day before.
**What we see:**
- The collection has nested sub-documents (`client`, `medicationResponse`, `analysis`, `status`, etc.) that Metabase auto-unfolds into `Parent: Child` columns.
- Users in the sandboxed group now only get the **top-level scalar columns**; every unfolded nested column is gone. Rows are filtered correctly.
- An admin (bypassing the sandbox), or the same question with the security removed, sees **all** columns. So the question, field metadata, and unfolding are all fine — the columns are lost only on the sandboxed query path.
**Already tried (no change):**
- Sync database schema
- Re-saving the Row and column security policy
- The unfolded fields are still active in Table Metadata and remain selected in the question
I also noticed the docs seem to disagree on whether Mongo sandboxing is supported: the Row and column security page says MongoDB supports row-level security, while the Data sandboxes page says sandbox permissions are unavailable for non-SQL DBs such as MongoDB. So I'm unsure whether this is a regression or a changed limitation.
**Questions:**
- Has anyone else seen unfolded Mongo fields vanish for sandboxed groups on v60/v61?
- Is there a known workaround beyond flattening the nested fields into top-level keys (e.g. a Mongo view that `$set`s the nested paths to top-level)?
(We've also raised this with support directly as a paid customer — posting here in case others have hit the same thing.)