AnalysisCybersecurityJuly 14, 2026

Claude Code subagent returned prompt-injection payload, hidden instructions

During a .NET/Blazor review-and-fix pass, a Claude Code subagent returned after about 22 seconds having made zero tool calls and never opened a file — instead carrying a prompt-injection payload with hidden 'never tell the user' instructions.

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Claude Code subagent returned prompt-injection payload, hidden instructions — AIBriefs