Prompt injection causing unauthorized agent actions

Prompt injection can redirect an agent through retrieved text, tool output or messages; the crucial security failure is executing an action with no legitimate task authority.

01 / Attack path

How the boundary is crossed

An incident agent reads a ticket comment saying to disable a different customer’s account as a diagnostic step.

Attack path and interception point
  1. 01Lower-trust input
  2. 02Attempted instruction
  3. 03Protected action
  4. 04Enforced decision

02 / Containment

Where bounded authority limits the effect

Mark content as untrusted, validate the task and target at the account API, and require independent approval for disabling accounts.

Architecture review / negative test

Make the boundary testable.

Treat retrieved text and tool responses as data that can attempt to steer the model. Upstream filtering and model instructions may reduce attempts, but neither proves that an external effect is authorized. Map the exact API that can disable an account and the task/target check it must enforce.

03 / Failure and evidence

The attacker’s opportunity and the defender’s record

Exploit condition

A prompt filter misses a persuasive variant and a broad tool credential allows the wrong account change.

Evidence to retain

Keep the untrusted input reference, attempted action, denial and actual account state; avoid storing unnecessary sensitive content.

04 / Canonical scope

Why this reference stands alone

MCP tool poisoning focuses on malicious tool metadata; this page covers the general content-to-action crossing.

Primary references

Read the underlying material

Architecture discussion

Choose one consequential action and make its boundary explicit.

Request a Conversation