Ethereum miners use the tools they have to organize transactions in blocks to benefit themselves and to obtain so-called "recoverable value" (MEV). This was pointed out by the analyst Frank Topbottom.
MEV has long been regarded as a theoretical method of data manipulation in a block, but with the blossoming of decentralized finance space the threat becomes real.
The analyst noticed a suspicious location of transactions in blocks added by such pools as SparkPool and F2Pool. Repeatedly, transactions sent from certain addresses, which, all other things being equal, would not have such priority because they used lower commissions, were ranked first. He also notes that smaller pools, such as 2Miners, Minerall Pool and EzilPool, which account for about 2% of the total hash rate, were seen more often in such practices.
In one case, the analyst found several signs at once that the specified transaction was not added to the block accidentally. The commission for its processing was insignificant and amounted to only 2 wei (1 Gwei = 1 billion wei). Under normal conditions, it is unlikely that such a transaction would ever be added to the network. In this case, it took 17 seconds.
The transaction was aimed at using the arbitration opportunity to earn $70 on a $2,800 transaction. Other users ignored this opportunity, considering it unreasonable, but the probable intervention of the miner allowed to use it effectively and reduce the spread in the market.
In other cases, the intervention of miners may not be so favorable, as they may be ahead of any other user who will send a profitable deal to the mempole of crypt currencies. An analyst assumes that in the future, the maintainers will compete for such transactions with each other and may even reorganize.
Remarkably, the problem will not be solved in Ethereum 2.0 either, as stackers will be able to perform the same manipulations. Possible ways to change the current system of including transactions into blocks are still being discussed by developers and are unlikely to be implemented in the near future.