Ethereum co-founder Vitalik Buterin called for prediction markets to use multiple independent data feeds on April 23 after a Polymarket weather dispute in Paris. He remarked on X after a controversy over airport temperature readings revived concerns about how decentralized markets settle real-world bets.
Buterin said a median of three independent sources should be mandatory, linking the Paris case to an earlier dispute involving Myrnohrad. The latest controversy followed allegations that a bettor used a portable heat source near a Météo-France sensor at Paris-Charles de Gaulle Airport.
French authorities have not publicly confirmed that detail, but the forecasting office flagged suspected tampering and referred the matter to police.
Initially, Polymarket’s two weather markets tracked the highest temperature in Paris on April 6 and April 15, using data from the Charles de Gaulle Airport station. According to Polymarket, the contracts used the station’s highest recorded temperature in degrees Celsius.
However, French outlet BFMTV reported Monday that the temperature briefly jumped above 21 degrees Celsius on April 6, then fell back almost at once. That market later settled, with the winning side taking more than $16,000.
Bubblemaps flagged a similar anomaly in the April 15 contract. The analytics platform said the weather station stayed at 18 degrees Celsius for most of the day, then suddenly rose to 22 degrees Celsius before falling back.
In response, Bubblemaps analysts said nearby stations did not show the same spike. They added that one trader bought NO shares on “18°C” shortly before the move and exited with more than $21,000.
The pattern raised fresh questions about possible tampering. Prediction markets already face broader scrutiny over insider trading and potential violations of gambling laws.
On Polymarket’s current Paris temperature markets, the rules point to Weather Underground data for the Paris-Le Bourget Airport station. The rules also state that revisions made after the data is finalized are not considered.
Buterin, by contrast, argued that oracle systems remain fragile when settlement depends on one real-world input or a single institutionally controlled feed. His post called for a median of three independent sources, or more, in multi-source oracles for those markets.
(adsbygoogle = window.adsbygoogle || []).push({});In a similar case earlier this year, a Polymarket market asked whether Russia would capture Myrnohrad. However, the market was settled using an online map maintained by a research institute. Per reports, the map briefly showed the city as captured when it was not.
The institute later said the map change was an unauthorized, unapproved edit that was removed before the day’s normal workflow began. It also reported that the think tank apologized and fired an employee over the incident. Together, the Paris and Myrnohrad disputes sharpened concerns about single-source settlement across decentralized prediction markets.
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