Major cryptocurrencies, including Bitcoin (BTC) and Ether (ETH), slumped sharply today, Monday, December 1, 2025, as a high-profile security breach at the decentralized finance (DeFi) platform Yearn Finance triggered a fresh wave of panic and sell-offs across an already fragile global crypto market.
The incident, which occurred late on Sunday, November 30, exacerbated the bruising decline seen throughout November, pushing Bitcoin’s price further below the psychologically key $90,000 level and dragging other major altcoins down with it.
The immediate catalyst for the market plunge was the disclosure by the DeFi aggregator Yearn Finance of an “incident” involving its yETH liquidity pool.
Blockchain security firms quickly confirmed that the attackers exploited a vulnerability in a custom smart contract related to the yETH pool, allowing them to mint a near-infinite amount of yETH tokens. This process effectively flooded the pool with invalid supply.
The total loss from the exploit is estimated at $9 million by security experts like PeckShield. The attackers profited by draining liquidity and siphoning off approximately 1,000 ETH (valued around $3 million), which was immediately routed through the crypto mixer Tornado Cash to obscure the trail.
Yearn Finance confirmed that its main V2 and V3 Vaults, which hold the majority of user funds, remain secure, stating the vulnerability was isolated to an older, custom stableswap pool.
The breach quickly rippled across the market, highlighting the fragility of investor sentiment in the decentralized space with Bitcoin slipping more than 5% in early trading, falling close to $86,000, extending its losing streak from November. Ether (ETH) also shed around 5.5%, trading near the $2,800 mark.
The sudden downturn triggered a massive wave of liquidations, with data showing that over $400 million in leveraged crypto futures positions, predominantly “long” bets expecting prices to rise, were wiped out. This cascading liquidation effect amplified the price decline across the board. .
The Yearn Finance hack, coming just weeks after the Balancer DeFi protocol suffered a $116 million exploit, underscores the fundamental Achilles’ heel of the decentralized finance movement: Smart Contract Vulnerability. Hence, TheLink News posits that the problem is twofold, namely, complexity and custom code and market structure.
For instance, DeFi protocols often rely on highly complex, interoperable smart contracts, frequently using custom or forked code. This complexity makes comprehensive auditing exceptionally difficult. The Balancer exploit, for instance, occurred despite the protocol undergoing over ten audits. The Yearn exploit was also attributed to a custom contract version.
Also, the rapid deployment of funds in the crypto market, coupled with high leverage, means that security incidents, even relatively contained ones like the $9 million Yearn loss, can trigger disproportionate market fear. Traders know that a flaw in one major protocol can expose others using similar code, leading to a generalized flight to safety and liquidity withdrawal.
This incident reinforces the need for Nigerian and global investors to exercise extreme caution in the DeFi space. While DeFi promises high returns, the lack of central regulatory oversight means that technical security, or the lack thereof, is the only real guarantor of asset safety. The market will remain fragile until the industry proves it can enforce rigorous, bug-proof code standards that eliminate these “infinite minting” and “oracle manipulation” flaws.
