A third-party vendor compromise discovered Thursday allowed attackers to inject a malicious script into Polymarket’s frontend, affecting multiple users.
Blockchain analyst Specter said the malicious script appeared to facilitate a phishing attack that drained an estimated $2.94 million from at least 11 Polymarket user wallets.
Polymarket said on X that the compromise has been contained and that the affected dependency has been removed. It added that users would be fully refunded.
Cointelegraph has approached Polymarket for comment but did not receive a response before publication.
The attack was the 89th reported crypto security breach of the second quarter, according to DefiLlama data, extending the most-hacked quarter on record by incident count.
Source: Specter
Crypto exploit losses reach $74.9M across 29 June incidents
Crypto exploit losses climbed to $74.9 million across 29 reported incidents in June, surpassing May’s $60.5 million total but remaining far below April’s $644 million, according to DefiLlama data.
Total value hacked by monthly sum, 1-year chart. Source: DefiLlama.
The largest June incidents included the $36 million Humanity Protocol exploit, the $4.7 million Secret Network bridge exploit, two separate Aztec exploits worth $2.1 million each and a $1.7 million bridge exploit on Taiko.
Related: About 60% of World Cup bettors on Polymarket are first-time crypto users
Over the past 30 days, private key compromises accounted for 43% of reported exploit losses, making them the leading attack vector, according to DefiLlama. Fake proof exploits accounted for 10%, followed by reverse MEV honeypots at 8%, which present deceptive trading opportunities to lure and manipulate automated trading bots.
About a month before Polymarket’s latest attack, the prediction market disclosed a separate $600,000 exploit that was traced to a six-year-old private key used for internal top-up operations. Josh Stevens, Polymarket’s vice president of engineering, said the platform’s contracts and user funds remained safe and that all permissions tied to the key had since been revoked.
Total value hacked by technique over the past 30 days. Source: DefiLlama
Polymarket currently holds over $450 million in total value locked, up 301% from $112 million a year ago, according to DefiLlama.
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