A social services casework office asks why overshared SharePoint case files become visible to many staff through Copilot. What explanation fits?

Because Copilot retrieves content within a user's existing access, broadly shared SharePoint case files become Copilot-visible to everyone who inherited that access. A social services casework office asking why overshared SharePoint case files become visible to many staff through Copilot should use that explanation: oversharing expands what Copilot can surface through permissions. Claiming Copilot retrains its foundation model on shared case files misstates how Copilot works: it does not train on tenant content, it retrieves indexed SharePoint content at query time within the prompting user's existing permissions, so broad sharing expands retrieval without any model retraining. Claiming Copilot grounds answers with site owner permissions misstates access control: it retrieves only what the prompting user already has permission to access, not what a site owner can access, so broad sharing matters because it widens each staff member's own access. Claiming Copilot copies shared case files into staff chat history for reuse misstates retrieval: it does not duplicate files into chat for later reuse, it surfaces permitted indexed content dynamically per prompt, so visibility follows current SharePoint permissions rather than stored chat copies. Exam caveat: AB-900 tests the data-access implication that oversharing increases Copilot exposure at describe depth. Operational check: audit case library sharing links and group membership, remove overly broad access, and re-test Copilot with representative caseworker accounts to confirm visibility narrowed.