On February 15, a governance proposal on DeFi lending protocol Moonwell went live. One oracle was misconfigured. Within seconds, $1.78M in bad debt accumulated as automated bots exploited a pricing error — repaying \~$1 of debt to seize cbETH actually worth \~$2,200.

The story went viral because the pull request carried a familiar tag: Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

Our VP of Security & Trust, Shahar Madar, took a deep dive on what actually happened — and the “AI wrote a dangerous bug” narrative misses the point entirely. The PR went through GitHub Copilot review, OpenZeppelin Code Inspector, human approval, and 28 CI checks. All passed.

The more interesting finding: Shahar ran Claude against the same PR with no context, and it flagged the right oracle for the wrong reason — rated LOW, missed the actual mispricing entirely. Then he gave it one sentence of domain context. It came back CRITICAL, calculated the \~2,000x price collapse, and recommended blocking the merge.

Same model. Same code. One sentence made the difference.

The real risk of AI in financial infrastructure isn’t that it writes bugs — humans do too. It’s speed without validation.

🔗 Full breakdown on LinkedIn

Claude Opus 4.6 co-authored a $1.78M bug, one sentence taught it to catch it | Shahar Madar, VP Security & Trust @ Fireblocks