Memory Theft Attack Tricks Claude AI into Exfiltrating User Personal Secrets Through Web Navigation
Security researcher Ayush Paul demonstrated how Claude's memory system can be exploited to leak sensitive user data including full names, employers, and security question answers without any user interaction beyond a normal query. The attack leverages Claude's web_fetch tool and a specially crafted website that forces the AI to navigate an alphabetical link structure to spell out private information stored in conversation summaries and conversation_search results. By disguising the exfiltration as a Cloudflare-style authentication challenge for a fictional coffee shop, the researcher bypassed Claude's safety mechanisms and achieved reliable data leakage. The technique works because web_fetch allows navigation through links present on previously fetched pages, enabling the construction of an on-the-fly 'keyboard' of alphabetical paths. After responsible disclosure via HackerOne, Anthropic implemented a partial mitigation by disabling external link navigation in web_fetch, though the underlying memory exposure risk remains for other connected tools and services.
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