DBRefs are okForStorage in jsobj.cpp:891, but the code only checks for existence of $ref or $id. It should be stricter, checking for both $ref and $id.

Currently, these return true for okForStorage:

• {$id: 1}
• {$ref: 1}

But should probably return false as they are not valid documents.

This is used in many places to verify valid fields, including DBRefs.