More than half of “long-shot” bets on military action made on Polymarket are successful, according to a new report that suggests prediction markets could pose a bigger threat than previously recognized to the security of sensitive information.

Analysis by the Anti-Corruption Data Collective, a non-profit research and advocacy group, found that long-shot bets—defined as wagers of $2,500 or more at odds of 35 percent or less—on the platform had an average win rate of around 52 percent in markets on military and defense actions.

That compares with a win rate of 25 percent across all politics-focused markets and just 14 percent for all markets on the platform as a whole.

The research is likely to add to growing concerns among regulators and lawmakers about insiders placing bets on the timing and success of military actions, amid fears that this could reveal classified information in advance.