defi-attack-patterns

An attacker borrows a large amount via flash loan, swaps it on an AMM to skew the spot price, then exploits a protocol that reads that spot price as its oracle, all within one transaction. Protocols using getReserves() directly are vulnerable; TWAP or Chainlink oracles mitigate this.

An attacker deposits 1 wei for 1 share, then donates a large amount directly to the vault, inflating the share price. A victim's subsequent deposit rounds down to zero shares due to integer division, letting the attacker claim the entire vault balance.

Verify the code checks that price is positive, updatedAt is nonzero, the heartbeat interval has not elapsed, and answeredInRound matches roundId. On L2s like Arbitrum or Optimism, also check sequencer uptime, since frozen prices during sequencer downtime enable stale-price arbitrage.

Yes, if a protocol counts live token balances for voting without snapshots. An attacker borrows governance tokens, meets quorum, passes a malicious proposal, and returns the tokens in one transaction. Snapshot-based voting and timelocks prevent this.

Fee-on-transfer tokens cause protocols to overcredit deposits if they assume received equals sent amount. ERC-777 tokens introduce reentrancy via tokensReceived hooks, and rebasing tokens break cached balance accounting. Measure actual balance deltas instead of trusting parameters.