“polymarket's off-chain matching creates a $1.49 million loophole for traders to selectively invalidate orders”
Polymarket matches orders off-chain for speed but settles on-chain for finality. This paper identifies a consistency gap they call Ghost Fills — orders matched off-chain that fail during on-chain settlement. Across 1.95M reverted transactions, the authors document four attack vectors that let traders selectively invalidate orders, realizing $1.49M in profit with 24.3% of filled orders reverting during peak hours.
Some technical background helpful
Platforms mentioned: Polymarket