How a five-second trick let traders drain millions from Polymarket

Polymarket's New Rules: A Game-Changer for Crypto Markets

Polymarket, a popular prediction market, has announced a significant change to its rules to prevent traders from manipulating prices and making money at others' expense. The platform will now use time-weighted average prices to resolve short-dated crypto contracts, making it harder and more expensive for traders to move prices.

This change is a direct response to research and trader complaints highlighting widespread settlement manipulation on Polymarket's five-minute crypto markets. A study of five-minute bitcoin contracts found patterns of large last-second Binance trades that appeared to move prices before settlement, with most resulting losses in likely manipulated windows borne by retail traders.

The new system, which uses Chainlink Data Streams and short TWAP windows, mirrors safeguards used by rival platform Kalshi, which relies on regulated price indexes and moving averages to make brief price distortions harder and costlier. Polymarket has replaced the single-price snapshot used to resolve short-dated crypto contracts with a time-weighted average price, or TWAP, after months of trader complaints and research identifying hundreds of accounts whose activity was consistent with settlement manipulation.

The researchers had found that 821 accounts made $8.2 million in settlement windows they classified as likely manipulated, prompting criticism that Polymarket's rules let a small number of traders profit at others' expense. To protect market integrity in its crypto up/down markets, Polymarket is updating how these markets resolve.

The Problem with Single-Price Snapshots

Single-price snapshots are a common practice in prediction markets, where the price of a contract is determined at a single point in time. However, this approach can be vulnerable to manipulation, as traders can move prices in the final seconds before settlement to force the market to resolve in their favor.

The Solution: Time-Weighted Average Prices

Time-weighted average prices, or TWAPs, are a more robust approach to resolving short-dated crypto contracts. By using a time-weighted average, Polymarket can reduce the impact of last-second trades and make it harder for traders to manipulate prices.

The Impact on Traders

The change to TWAPs will have a significant impact on traders who have been exploiting the single-price snapshot system. Traders who have been making money by manipulating prices will now face a more challenging environment, where their actions are less likely to succeed.

Conclusion

Polymarket's decision to switch to TWAPs is a significant step towards preventing market manipulation and ensuring fair and accurate prices. The change will have a positive impact on traders who have been affected by the single-price snapshot system and will help to maintain the integrity of the crypto markets.