What is Planted canary?
A harmless marker deliberately inserted so that if it later shows up somewhere it should not, you have undeniable proof of a data flow or injection.
Planted canary: A harmless marker deliberately inserted so that if it later shows up somewhere it should not, you have undeniable proof of a data flow or injection.
In plain language
A canary is a tracer dye for security testing: a unique, benign value planted in one place so that observing it elsewhere proves something moved that should not have. It converts a suspicion into evidence.
SuperPentest uses a planted canary to prove second-order prompt injection: a marker injected through one channel and observed reaching a privileged tool call through another is a real injection, not an inference from a suggestive reply. Canary methodology →
A concrete example
To prove an AI assistant can be hijacked through a document, the test plants a unique string — say CANARY-7f3a — inside the file and instructs nothing else. If that exact string later appears in an outgoing API call the assistant made, the data flow is undeniable: the document’s content drove a tool action. The canary turns “the model seemed to comply” into hard evidence.
Related
Prompt-injection canary research → · Second-order prompt injection →
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