GoPlus: Polymarket Hacked, Off-Chain and On-Chain Transaction Result Synchronization Mechanism Has Flaws

CycleProphet · 2026-02-20T04:41:14+00:00

Polymarket prediction market platform was hacked due to design flaws. The attacker manipulated the nonce to invalidate on-chain transactions, resulting in user losses. Users are advised to suspend automated trading tools, verify transaction statuses, enhance wallet security, and monitor official announcements.

CycleProphet

2026-02-20 04:41:14

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Deep Tide TechFlow News, February 20 — According to the GoPlus Chinese community, the prediction market platform Polymarket was hacked due to a design flaw in the synchronization mechanism between off-chain and on-chain transaction results in its order system. The attacker manipulated nonces to cause on-chain matched transactions to be canceled or invalidated before finalization, while off-chain records remained valid, leading to API false reports, affecting trading bots like Negrisk and causing user losses.

The attack process is analyzed as follows:

The attacker submits/matches large reverse trades with a market-making bot on Polymarket’s off-chain order book.
The attacker constructs transactions with forged/repeated nonces or exploits on-chain nonce competition, ensuring the on-chain transaction will revert.
Polymarket’s API returns “Trade Successful” to the bot before on-chain confirmation, causing the bot to believe the position has been hedged, even though the on-chain state has not yet changed.
The attacker then exploits the exposed direction by executing a real on-chain transaction, achieving “risk-free” profit.
Since the revert occurs at the blockchain layer, Polymarket’s fees do not explode, making the attack cost manageable and repeatable.

GoPlus recommends users pause automated trading tools, verify on-chain transaction statuses, strengthen wallet security, and closely monitor official Polymarket announcements.

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