Claude Opus 4.6-linked oracle bug causes Moonwell smart contract exploit and $1.78M loss on cbETH market

On February 15, 2026, DeFi lending protocol Moonwell discovered a critical oracle misconfiguration on its cbETH Core Market on Base, which it linked to Solidity code partially authored by Anthropic's Claude Opus 4.6. The bug priced cbETH at about $1.12 instead of nearly $2,200, enabling liquidations and abnormal borrowing that left users facing an estimated $1.78 million in losses across cbETH, WETH, and USDC positions. The incident, which followed Bithumb's multi-billion-dollar reward misassignment on February 6, has intensified debate around AI-assisted "vibe coding" and the limits of human oversight.