---
id: "willison-lethal-trifecta"
title: "The lethal trifecta for AI agents"
creator: "Simon Willison"
creator_url: "https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/"
url: "https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/"
level: "intermediate"
level_max: "advanced"
category: "security-and-red-teaming"
subcategory: "agent-and-tool-security"
region: "West"
license: "closed"
license_scope: "linked-resource"
models: ["any"]
source_date: "2025-06-16"
date_added: "2026-10-18"
---

[Security And Red Teaming](/security-and-red-teaming/index.md)

# The lethal trifecta for AI agents

by [Simon Willison](https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/)

[Read the original →](https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/)

A defensive framework for recognizing risky combinations of agent capabilities and untrusted inputs.

This security discussion identifies a risky combination of sensitive access, untrusted inputs and communication capabilities. We link the analysis for defensive design; no attack instructions or payloads are reproduced here.

Level: [Intermediate](/levels/index.md#intermediate) to Advanced
Models: any
Category: [Security And Red Teaming](/security-and-red-teaming/index.md)
Tags: [security](/tags/security/index.md), [prompt-injection](/tags/prompt-injection/index.md)
Source date: 2025-06-16
Added: 2026-10-18
Last verified: 2026-10-18
Status: ok
Prerequisites: No-code explanation, but assumes tool-using agents and data access; the supplied rubric places it at Intermediate.
Subcategory: [agent and tool security](/security-and-red-teaming/agent-and-tool-security/index.md)
Region: West
Original language: en
Access: free
Resource reuse: closed: No general open-reuse grant established from the inspected page. Closed is the conservative index bucket, not a legal finding; the resource is publicly readable. [Facet definitions](/about/index.md#facets)

Summary in our own words. Rights remain with the original creator. [Credit and correction policy](/about/index.md#credit-policy).

[Plain-text Markdown copy](/security-and-red-teaming/agent-and-tool-security/willison-lethal-trifecta/index.md)