Arcus, a decentralized exchange running on Robinhood Chain, said it identified and fixed an accounting bug that allowed a user to withdraw funds they were not entitled to. The exchange covered the resulting shortfall of approximately $2 million from its own treasury, according to a company statement.
The bug was detected on November 9 and patched within one hour, Arcus said. The company stated that no user balances were affected and that trading and withdrawals are operating normally.
What happened
The issue was an accounting error in the system that tracks ownership, where the numbers stopped matching reality. Arcus has not publicly described the specific mechanics of the bug, nor has it said whether the withdrawal was a deliberate exploit or an opportunistic action by a user who noticed an inflated balance.
The company’s statement emphasized three points: the bug was caught quickly, the gap was filled, and customer funds were untouched. By absorbing the loss at the company level rather than socializing it across traders, Arcus kept customer balances whole but drew down reserves held for such situations.
About Arcus
Arcus launched in beta around June or July 2026 and focuses on on-chain trading of tokenized stocks. The exchange offers zero-fee spot trading of stock tokens around the clock, allowing them to trade on weekends and outside normal market hours. It also runs cross-margined perpetual futures with leverage of up to 50x.
Cross-margin pools a trader’s collateral across positions rather than isolating it per trade. While capital efficient, it means the accounting system must track many moving parts simultaneously. According to research, the exchange is built by the dYdX team in partnership with Robinhood Crypto and is designed to operate outside the regulatory boundaries of the US, UK, and Canada.
Around November 5 to 7, just days before the incident, Arcus expanded multi-asset collateral support to all traders, allowing a wider range of assets to be posted as margin. Arcus has not linked the bug to that rollout.
What it means for traders
For current users, the immediate takeaway is that balances remain intact and withdrawals function. Covering the shortfall from treasury signals that customer funds are prioritized, even at the cost of the company’s reserves.
However, the existence of the bug raises questions for an exchange offering up to 50x leverage on cross-margined positions, where accounting errors can compound quickly. Key items to watch include whether Arcus publishes a detailed post-mortem explaining the root cause and process changes, whether it addresses recovering the funds from the user, and how the incident affects the pace of new feature rollouts.
