On October 29, 2026, prediction market Polymarket suspended international trading for one hour following a security breach involving third-party vendor DebugBear. Malicious code served via DebugBear's network hijacked user sessions and drained $2.7 million from 726 wallets. Polymarket committed $3.9 million to repay stolen funds and trading pause losses, fully reimbursing 689 accounts by October 30. The incident marks Polymarket's second vendor-related breach since June 2026.
Trading pause and platform operational response
- ▪Polymarket temporarily halted trading on its international platform for approximately one hour
- ▪During the October 29, 2026 trading halt, Polymarket placed its platform into cancel-only mode, allowing users to cancel orders while blocking new trades
Security breach mechanism and execution
- ▪Prediction market platform Polymarket suffered a security breach impacting its international platform
- ▪Report URI's Scott Helme said the October 29, 2026 security breach involved compromised web-monitoring vendor DebugBear, which served a malicious script from its content delivery network
Reimbursement pledges and identity check requirements
- ▪Polymarket drew pushback for requiring larger theft victims to complete identity checks, release agreements, and non-disparagement clauses to receive reimbursements
- ▪As of October 30, 2026, Polymarket had fully repaid 689 of 726 affected user wallets, with the remaining 37 awaiting verification
- ▪Polymarket pledged $3.9 million total to reimburse $2.7 million in stolen user funds and $1.19 million in losses tied to Polymarket's trading pause
Previous vendor attack in June 2026
- ▪Polymarket's October 29, 2026 security breach marked Polymarket's second major vendor-related security breach in four months, following a June 25, 2026 attack that drained roughly $3 million
- ▪The security breach at Polymarket was executed via a compromised third-party marketing tag that injected code targeting wallets holding over $100,000
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