Measured only for what they say out loud, frontier assistants look private; measured for what a reply implies, inferential leakage still ran at 16 to 25 percent even under a privacy-aware system prompt
AspireAI community · arXiv (Huang, Fu, Meng & Chaudhuri)
InferPriv targets a gap in how personal-agent privacy is evaluated. Direct leakage - the agent explicitly stating a secret - is what existing benchmarks measure. Inferential leakage is different: the reply never names the sensitive attribute but leaves cues an honest-but-curious recipient can read off it. The benchmark asks whether a third party can infer a user's sensitive attributes from a routine task reply, and inferential leakage exceeded direct leakage across every model and prompt tested.
The sharpest result is the privacy-aware condition. GPT-6.1-Sol, Sonnet-5.5 and Gemini-3.8-Flash all reach near-zero direct leakage when given a privacy-aware system prompt, yet the inferential leakage rate stays between 16.2 and 25.2 percent. Any evaluation that only checks for explicit disclosure is therefore understating the risk substantially.
The limitation is that the benchmark simulates the recipient rather than using real recipients, and it covers five frontier models on synthetic tasks, so the absolute rates are indicative of the gap between the two measurement styles rather than a field estimate.
https://arxiv.org/abs/2610.34640
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