Flash loan attacks.

A flash loan lets someone borrow a large sum with no collateral, as long as they repay it inside the same transaction. Used as an attack, the borrower takes the loan, distorts a price, drains a pool, and repays before the transaction closes. These have cost decentralized finance hundreds of millions.

The attack only works if many steps chain inside one transaction. On Ethereum, a single transaction can call several contracts in sequence, so borrow, manipulate, and repay fit together. A new XRPL proposal notes that chaining is not possible there. Each XRPL transaction is one self-contained action.

The cost is composability, the flexibility that also powers legitimate Ethereum applications. XRPL trades it for a smaller attack surface.