The five-second exploit
Traders found a way to move prices in a burst that lasted only five seconds. The tactic let them pull out millions before the market could react. Onchain analysts had publicly flagged the vulnerability for months, warning that the platform's price updates were open to manipulation. Their warnings went unheeded until the drain happened.
The exploit worked because Polymarket's prices updated instantly. A trader could place a large order, move the price, and then cash out within the same five-second window. The quick move made it possible to drain funds before anyone could adjust. Onchain analysts had even posted detailed breakdowns of how the trick would work, urging the platform to fix the pricing model. Nothing changed until the drain hit.
Why time-weighted pricing
Time-weighted prices average out price changes over a set period. A single sudden spike won't stick if it doesn't hold up over the whole window. That makes it much more expensive to push a price artificially, because you'd have to keep it elevated for longer than five seconds. Polymarket is implementing this change to make those artificial pushes too costly.
The new system doesn't eliminate price movement, but it smooths out the sharp edges. Instead of reacting to a single trade, the price reflects the average over a defined time frame. That means a trader who wants to manipulate the market has to commit more capital and more time to the effort. The five-second burst that worked before would now have to hold for a longer stretch, which is a much riskier bet.
