Bare Key Elicitation with Trailing Colon - ATR-2026-02009 (b82a47ae-0a2a-5c8b-a04c-e639ace76ede)
Detects prompt-injection attempts that elicit secrets or credentials by presenting a bare key/secret label followed by a trailing colon (or equals/opening-bracket) with no value, inviting the model or a downstream agent to fill in the missing secret. Mined from red-team false negatives where attackers avoid explicit "give me your API key" phrasing and instead plant a dangling "SECRET_KEY:" / "secret key:" style prompt that pattern-completion or instruction-following tends to satisfy. Scoped to untrusted-input channels (user turns and tool responses carrying external content); a schema-block-preceding "key:" from a trusted system prompt is a plausible, if rare, benign edge case and is out of scope for this rule.