Sonne Finance, a decentralised lending protocol on the Optimism blockchain, fell victim to a flash loan attack, resulting in a loss of approximately $20 million. This attack exploited a known vulnerability in Compound v2 forks, particularly targeting the donation function logic.
The attacker exploited the protocol’s governance and collateral factors by manipulating a governance proposal and altering collateral factors to favour the exploit. This allowed them to donate borrowed funds, causing a significant shift in the protocol's financial state, leading to the theft of $20 million. The vulnerability mirrored an exploit that had previously impacted Hundred Finance, another Compound v2 fork.