Ostium halted all trading on Wednesday after an attacker allegedly manipulated its oracle system and drained as much as $18 million in USDC from the protocol’s OLP liquidity vault.
The Arbitrum-based protocol offers perpetual trading tied to real-world assets. It previously raised about $27.8 million from backers including General Catalyst and Jump Crypto.
Blockaid details the exploit, while loss estimates vary
Onchain security firm Blockaid said the attacker “used a registered PriceUpKeep forwarder and future-dated authorized oracle reports to create artificial trade profit, triggering a ~$18M USDC payout from the vault.”
Blockaid published both the exploit transaction and the attacker address on Arbitrum. The transaction cited in its disclosure, 0x359f8c05...d4870e0, is confirmed onchain.
There is still no single loss figure accepted by all parties. Blockaid put the payout at roughly $18 million. Independent onchain observers estimated a smaller number, with some placing the drained amount near $11.86 million. Ostium has not published its own accounting of the loss.
According to DefiLlama data, the protocol had about $63.3 million in total value locked shortly before the attack. Even the lower-end estimate would represent a meaningful share of the vault’s balance.
Ostium confirms the incident and pauses markets
Ostium acknowledged the issue and suspended trading. In a post on X, the protocol wrote: “We are aware of the issue with the OLP vault. We have paused all trading. The team is investigating.”
Ostium allows users to trade perpetual contracts on assets such as gold, oil, equity indices, and foreign exchange directly from a crypto wallet, with settlement in USDC on Arbitrum, a Layer 2 network. According to the protocol, the OLP vault has supported more than $33 billion in cumulative trading volume across more than 50 markets.
The attack appears to have hit a trusted part of the system
The component Blockaid says was used in the exploit sat inside a part of the system that Ostium had previously told security researchers to treat as safe. In the protocol’s bug bounty scope, all registered keepers, including PriceUpKeep, “and their forwarders are assumed to be trusted and operating correctly,” while findings that require a compromised or malicious keeper fall outside the program.
The mechanism of the attack and the top-end loss number remain Blockaid’s stated findings and have not been independently reconciled. Blockaid’s post referred to a “registered forwarder” and “future-dated authorized oracle reports.” It did not say a private key had been compromised, even though some descriptions of the incident have framed it that way.
Ostium has not said how the attacker gained the ability to submit those reports, and it has not released a final loss tally.
Another case involving keeper and oracle infrastructure
The incident adds to a string of exploits involving automated keeper and oracle systems that DeFi protocols use to bring real-world prices onchain.
Summer.fi lost about $6.04 million in a share-price manipulation on July 6, according to its post-mortem. In April 2025, an attacker drained roughly $7.5 million from KiloEx across three chains by impersonating a trusted keeper and feeding false prices to the protocol, a structure that Blockaid said resembles what happened at Ostium.
The pattern highlights a repeated weakness for protocols that settle trades against offchain data. The delivery machinery for those prices is often trusted by default. Once that layer is controlled, a protocol can end up paying out on trades that never actually made money.