𝕾𝖔𝖓𝖞𝖆𝕯 ⚡

On October 31, THORChain halted trading on several blockchains. An Ethereum block reorg caused THORChain to pay out 10 ETH that a vault never received. The automatic solvency checker caught the shortfall and halted ETH swaps. Within approximately two minutes, node operators halted ETH transaction signing, so no further ETH could leave the vaults. Node operators then halted all chains as a precaution so core developers could investigate. The 10 ETH has been returned by the user to make the vault solvent again. Breakdown of what happened and next steps: At 11:34 UTC Oct 31, Ethereum had a one-block reorg. A 10 ETH deposit to one of the vaults sat in the dropped block and never landed on the canonical chain. THORChain had already observed and credited that deposit. The swap missed its price limit and was refunded, so the vault paid out 10 ETH it never received. The sender's real deposit was refunded as well. Every node detected the reorg. But the re-check that should have removed the deposit could not get a clear answer in time, so it was finalized. The solvency checker halted ETH swapping automatically, then three node votes halted all ETH outbound payments. All chains were then halted by three node votes as a precaution. Now that this is public knowledge, every time there is a block re-org on an external chain, a malicious actor could perform a new transaction with the same nonce and would be paid funds by the THORChain vaults. Note: Three node votes can trigger emergency halts to protect network solvency. However, that action can be reversed by four counter node votes, then five node votes can reverse the reversal, and so on, maintaining a balance between decentralization and rapid emergency intervention. Halting a chain does not give those nodes control of the assets. Core developers have been working on the necessary fixes. Nodes will decide to re-enable chains as they are deemed safe. Trading blockchains: AVAX, BASE, RUNE, XRPL Halted blockchains: ATOM, BCH, BSC, BTC, DOGE, ETH, LTC, SOL, TRON, ZEC

One of the biggest $ZEC swaps on THORChain so far: 0.365 $BTC for 24.7 $ZEC, about $29.6K. The $ZEC pool held 22.9 $ZEC when the swap started. The swapper received more than the pool held. THORChain streamed it: 1,300 sub-swaps over 1h58, with arbitrageurs refilling the pool between them. The pool never dropped below 22.2 $ZEC. THORChain's fee came to about 0.22%, and the app the swapper used added 1.25%. About 15% of the deposit came back. The swapper had set a price limit, and midway through $ZEC got 5% more expensive in the pool. Streaming checks that limit on every sub-swap. 197 of them would have delivered less $ZEC than the limit allowed, so THORChain skipped them and refunded 0.065 $BTC instead of filling at a worse price. Once the price came back, the rest of the swap went through. $ZEC is still in a progressive rollout. The pool is kept small while the integration is tested on mainnet, and liquidity deepens once that goes well. With streaming, a thin pool means a longer wait, not a worse price. thorchain.net/tx/9AD0223E5CE…