Simon Willison names the lethal trifecta

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Named the lethal trifecta — the rule that data theft becomes possible when three things come together in one agent: access to private data, exposure to untrusted content, and the ability to communicate externally

Why it matters

Became the practical checklist of agent security discussions. Vendor documents and security guides adopted the three-part distinction as is

Source — Primary sources first; secondary reports are labelled “Press”

Officialsimonwillison.nethttps://simonwillison.net/2025/Jun/16/the-lethal-trifecta/

Added in Week 35, 2026 · See that week

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  1. Previous stopTrail of Bits discloses the line jumping vulnerability
  2. This record · stop‘Lethal trifecta’
  3. Next stopClaude for Chrome
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