~/talk

Detecting Data Leaks in Multi-User LLM Apps via Automated User-Scoped Taint Analysis

Talkat SOAP 2026 · on Tuesday, 2026-06-16· [security, large-language-models]
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Finds a real Open WebUI bug that leaks one user's PDF-derived embeddings into another user's session and measures that 42% of popular open-source LLM apps support multi-user mode. Implements Access Flow Guard (AFG) that auto-identifies user-scoped sources via a function-signature dataset (OpenAI, Anthropic, Gemini), tags inputs with permissions in a Multi-User, Multi-Permission (MUMP) setup, and propagates tags with Scoped Taint Pointer Analysis (STPA). Prototype reports true positives and zero false positives on the evaluated apps.

AI-written summary · about

  1. 0:00Detecting LLM data leaks
  2. 2:10Open WebUI leak bug
  3. 5:22Limitations of taint tools
  4. 8:50User-scoped taint analysis
  5. 12:28Cache-based data leak example
  6. 14:36MUMP and STPA for scope overlaps
  7. 16:43Prototype results and future work
  8. 17:45Q&A
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