French authorities are investigating what appears to be the first known case of physical manipulation of real-world infrastructure to win prediction market bets, as US prosecutors separately charged a US Army special forces sergeant with using classified information to net $409,000 from bets on the capture of Venezuelan leader Nicolás Maduro — the latest in a string of incidents exposing structural vulnerabilities in blockchain-based betting platforms.
Manipulating the Weather
On the other side of the Atlantic, Météo-France filed a police complaint this week after detecting suspicious temperature spikes at Paris-Charles de Gaulle airport that coincided with highly profitable, well-timed bets on Polymarket, the Financial Times reported yesterday. On April 6 and April 15, temperature readings at the airport spiked by several degrees Celsius within minutes — jumping to 22 °C despite ambient conditions suggesting 18 °C — triggering payouts to traders who had wagered on those exact readings.
One wallet made $13,990 on a stake of less than $30 after betting that Paris temperatures would hit 21 °C, with an implied probability of just 0.2% at the time the bet was placed. Another wallet turned $119 into more than $21,000 betting that temperatures would exceed 18 °C at 0.5% implied probability. On both days, trading volume in Polymarket's Paris temperature market exceeded $500,000 — more than double typical daily volume.
"In light of physical findings on one of our instruments and the analysis of sensor data, Météo-France has indeed been led to file a complaint for interference with the operation of an automated data processing system with the Air Transport Gendarmerie Brigade in Roissy," the agency said, declining further comment, FT reported.
Members of Infoclimat, an online weather forum whose users track Météo-France data almost in real time, first flagged the anomalies on April 6 but initially assumed sensor glitches. "We thought it was an issue with the sensors... You can have sudden temperature changes at sundown when there is a storm as well. But the weather situation didn't explain what was happening," said Sébastien Brana, who runs the forum. "It became clear there was something else going on when it happened again on April 15."
Online forums used by weather enthusiasts discussed whether a battery-powered hairdryer may have been deployed to manipulate the sensor. Polymarket has since switched its Paris temperature resolution metric from Charles de Gaulle to Paris-Le Bourget airport, but has not cancelled the resolved contracts or refunded bets.
US soldier charged
The French case broke as US prosecutors unsealed an indictment against US Army Master Sgt. Gannon Ken Van Dyke, a communications specialist supporting the Joint Special Operations Command (which oversees Delta Force and SEAL Team Six), stationed at Fort Bragg, North Carolina.
According to the indictment, Van Dyke placed more than $33,000 in bets on Polymarket tied to the Maduro capture operation within hours of President Trump's January 3 Truth Social post announcing that Maduro and his wife had been "captured and flown out of the Country." The bets hit, generating $409,000 in winnings. Van Dyke was charged with unlawful use of confidential government information, theft of nonpublic government information, commodities fraud, wire fraud, and engaging in monetary transactions from unlawful activity.
"Prediction markets are not a haven for using misappropriated confidential or classified information for personal gain," said US Attorney Jay Clayton in the Southern District of New York. "The defendant allegedly violated the trust placed in him by the United States Government by using classified information about a sensitive military operation to place bets on the timing and outcome of that very operation, all to turn a profit. That is clear insider trading and is illegal under federal law."
Last month, we published our enhanced market integrity rules to combat insider trading.
— Polymarket (@Polymarket) April 23, 2026
When we identified a user trading on classified government information, we referred the matter to the DOJ & cooperated with their investigation.
Insider trading has no place on Polymarket.…
Polymarket said in a statement on X: "Insider trading has no place on Polymarket. Today's arrest is proof the system works."
Trump, asked about the case at an Oval Office event, offered a rueful assessment. "That's like Pete Rose betting on his own team," he said, drawing a parallel to the baseball legend banned from the sport for gambling. "The whole world, unfortunately, has become somewhat of a casino, and you look at what's going on all over the world, in Europe and every place, they're doing these betting things. I was never much in favor of it. I like it conceptually, but it is what it is."
Israeli authorities separately indicted two reservists in February for allegedly using classified information to bet on military operations. A CNN investigation found one trader made nearly $1 million over two years from bets on US and Israeli military actions against Iran, including a $553,000 profit from a bet placed moments before an Israeli airstrike killed Iran's Supreme Leader....
Structural vulnerabilities
The incidents highlight a fundamental tension in prediction markets: their settlements rely on external data sources — government agencies, news organisations, think tanks — over which they have no control, and whose integrity can be compromised through physical tampering, insider access, or social pressure. Polymarket does not require most accounts on its international site to provide identification documents, meaning the company itself may not know who is behind a given wager.
Traders on Polymarket have previously threatened an Israeli journalist to alter his reporting to align with their bets. Other active markets currently resolve based on maps produced by the Institute for the Study of War tracking Ukraine's frontlines. Neither the journalists, the think tank, nor Météo-France have any say in whether their outputs become arbiters of financial outcomes on the platform.
The rapid growth of prediction markets — Polymarket is reportedly in fundraising talks at a valuation up to $15 billion — has outpaced the infrastructure needed to ensure data integrity. Goldman Sachs and other institutional traders are already using Polymarket data to inform their own positions, meaning manipulation in thin markets can now propagate to mainstream finance.
Regulatory scrutiny is growing. In the UK, the Gambling Commission considers Polymarket and its US-regulated rival Kalshi to be unlicensed betting operators. The DOJ's prosecution of Van Dyke signals US authorities are prepared to apply insider trading law to prediction market activity — a legal theory that remains untested but could fundamentally reshape the industry's operating model.
