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Large Language ModelsAI Safety & AlignmentZenn AI/MLPublished: Oct 28, 2026, 01:00 JST

AI Security Lab tests role-based access in RAG: leaks persist

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AI Security Lab tests role-based access in RAG: leaks persist

3 Key Points

  1. What happened

    AI Security Lab ran ten tests (PI-062-01 to PI-062-10) on a mock internal RAG setup; after department-and-role Retriever controls, restricted documents stayed out of the LLM context, but personal mobile numbers still appeared in answers.

  2. Why it matters

    Filtering which documents a user can retrieve does not stop over-disclosure of sensitive fields inside permitted documents, so access control and output checks appear to need separate design.

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Context & Analysis

The experiments move in stages. With no access control at all (PI-062-01), answers to a general user included personal mobile numbers, HR evaluation information and a mock API key from production-configuration documents. Simply telling the LLM a user's department and role (PI-062-02) left unauthorized documents retrievable, so the lab concluded authorization must be enforced by the application, with prompt instructions only as a supplement.

Once the Retriever filtered by department (PI-062-03) and then by role and document (PI-062-04), sales general staff could not retrieve manager-only sales strategy documents while sales-manager01 could. That did not solve disclosure within permitted documents: sales general staff could still obtain personal mobile numbers from customer-contact documents they were allowed to see. The lab separates three questions that a final answer alone cannot distinguish — whether retrieved documents are authorized, whether the documents actually passed to the LLM are authorized, and whether the answer itself is appropriate and grounded.

In the prompt comparison (PI-062-10), the hardened prompt instructing the model to treat retrieved text as untrusted data coincided with fewer personal-number outputs, but the baseline also produced no attack markers, so the lab could not confirm improved injection resistance and noted that hardened runs still generated sales measures, plans and ROI/KPI specifics unsupported by source documents. It recommends authentication, Retriever authorization, context logging, prompt instructions and output validation as separate controls, and cautions that the results do not prove safety across all paths or inputs.

FAQ
Did adding department and role controls fully prevent data leaks?
No. After Retriever controls, restricted documents were excluded from search results and the LLM context in tested cases, but sales general staff could still get personal mobile numbers from permitted customer-contact documents.
Did a hardened prompt reduce personal information output?
In the comparison, the baseline prompt output personal mobile numbers 2 of 6 times, while the hardened prompt output them 0 of 6 times. The lab said the small trial count means it cannot claim a general effect or causal link.
Was indirect prompt injection blocked by the hardened prompt?
No attack marker was output in any of the 12 LLM calls, including under the baseline prompt, so the lab could not confirm an improvement from hardening on that measure.
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