Written by Stephen Katte⁠, Staff Writer. Reviewed by Felix Ng⁠, Staff Editor.

Written by Stephen Katte⁠, Staff Writer.

Reviewed by Felix Ng⁠, Staff Editor.

Polymarket denies data breach, says hacker is selling public data

Latest NewsPublishedApr 29, 2026

Polymarket Denies Data Breach Claims

A recent claim by a hacker that they had breached Polymarket’s customer data has been denied by the prediction markets platform. The hacker, using the pseudonym “xorcat,” posted on the dark web that they had stolen over 300,000 records, including 10,000 unique user profiles with full names, profile images, proxy wallets, and base addresses.

However, Polymarket has called the claims “complete and utter nonsense,” stating that the information posted by the hacker is already available online. The company emphasized that its data is publicly auditable, which is a feature of being on-chain, and that no data was leaked. Instead, the data can be accessed for free via Polymarket’s public endpoints and APIs.

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The so-called hacker claimed that the data was being posted because Polymarket didn’t have a bug bounty program. However, Polymarket has a live bug bounty program that started on April 16 and has received 446 reports as of Wednesday. Security experts have also expressed doubt about the claims, with one researcher stating that it appears “someone parsed data and is trying to present it as a [DB] leak.”

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“You compromised our platform by accessing publicly accessible API endpoints & on-chain data and *checks notes* are trying to sell the data we offer developers for free? Which VC paid you to post this?” Polymarket said.

In another post, the prediction market said: “Part of the beauty of being on chain is all our data is publicly auditable, this is a feature, not a bug. No data was leaked, it’s accessible via our public endpoints & on-chain data. Instead of paying for the data, you can access it for free via our APIs.”

Source: Polymarket 

Hacker claims over 300,000 records stolen 

The so-called hacker said the data was being posted because Polymarket didn’t have a bug bounty program. 

Related: Scammers use Gmail dot alias trick to spoof Robinhood in phishing scam

However, Polymarket has a live bug bounty program that started April 16 and has received 446 reports as of Wednesday.  

Source: Dark Web Informer 

Xorcat also said data was pulled via undocumented API endpoints, pagination bypass and CORS misconfiguration on Polymarket’s Gamma and CLOB APIs. The hacker claimed to have breached other prediction markets and planned to release the data over the next few days.

Several security experts have expressed doubt. Vladimir S, a threat researcher and chief security officer at Legalblock, said it appears “someone parsed data and is trying to present it as a [DB] leak. It does not seem probable to me.”

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• Scams & Cybercrime
• Polymarket
• Scams
• Hacks
• Data
• Social Media
• Dark Web
• Hackers