Balancer Protocol Hacked for $120 Million Due to Rounding Error

On November 3, 2025, the Balancer protocol was hacked, resulting in a loss of approximately $120 million across multiple blockchains, including Arbitrum and Ethereum. The attack exploited a dual vulnerability involving precision loss and invariant manipulation, specifically targeting the _upscaleArray function used for small transactions. This incident marks one of the largest exploits in the DeFi sector in 2025.