Matcha Meta has reported a significant security breach involving SwapNet, resulting in the loss of approximately $16.8 million in cryptocurrency. The breach primarily affects users who opted out of "One-Time Approvals." On the Base network, the attacker converted around 10.5 million USDC into approximately 3,655 ETH and has started transferring these funds to the Ethereum network. Users are advised to immediately revoke all approvals to individual aggregators that are not part of 0x's One-Time Approval contracts to mitigate further risks.