Polymarket's Bitcoin-Sale Ruling Sparks Dispute Over $80 Million in Bets

Polymarket’s five-minute Bitcoin up-or-down contracts relied on Chainlink oracle data tied to Binance spot prices to determine payouts. That design left settlement vulnerable to brief, relatively inexpensive price moves at the end of each contract. The episode highlights a broader weakness in ultra-short prediction markets: even when an oracle reports genuine market data, traders may still influence the underlying venue at the precise moment that decides the outcome.

Academic researchers found that more than 800 accounts traded Bitcoin on Binance during the final 10 seconds before Polymarket settlements, influencing oracle prices and generating about $8.2 million in profit. Retail traders absorbed 93% of the resulting losses, according to the study. Polymarket responded by introducing a 30-second time-weighted average price, or TWAP, for settlement and adding liquidity incentives, sharply reducing the scope for last-second price manipulation.

Decentralized prediction market Polymarket has been hailed as a truth machine. But a recent dispute over a contract asking whether MicroStrategy had sold Bitcoin exposed how such platforms’ determinations of fact can be highly vulnerable to after-the-fact rule interpretations, biased oracle voting and manipulation by large traders. It has also revived a regulatory debate over whether prediction markets should be treated as online gambling or financial derivatives venues.

The dispute began in May 2026, when MicroStrategy sold 32 Bitcoin before the May 31 deadline but did not report the transaction until June 1. Polymarket subsequently changed the rules and resolved the market as “No,” prompting fierce investor backlash. In July 2026, several traders who had backed “Yes” filed a class-action lawsuit against the platform in New York, alleging breach of contract and fraud and accusing it of depriving investors of legitimate gains through a biased decision.

Polymarket is a prediction-market platform where users trade probabilities based on event outcomes, and it has gradually expanded its range of crypto-asset contracts in recent years. These products do not involve buying or selling Bitcoin directly. Instead, users bet on whether its price will rise or fall over a brief period. The rapid influx of money into ultra-short-duration markets shows speculative activity spreading from traditional cryptocurrency exchanges to prediction markets.

As of July 20, 2026, daily trading volume in Polymarket's 5-minute and 15-minute Bitcoin price bets had surged to $60 million, making them among the platform's most active markets. Volume remained below that of major cryptocurrency exchanges, but the rapid buildup in turnover for short-duration contracts underscored strong market interest.