On May 20, 2026, the P2P decentralized exchange RetoSwap was exploited for approximately 7,000 XMR (~$2.7M) due to a critical vulnerability in its upstream Haveno trading protocol. The attack allowed a malicious actor to impersonate an arbitrator, enabling them to hijack multisig wallet creation before funds were deposited.
The exploit relied on a flaw in how the Haveno trade protocol handled message synchronization during the initial trade setup. When an attacker initiated a trade, they sent a fraudulent, out-of-order acknowledgment (ACK) message to the victim, effectively impersonating the platform's arbitrator.
This spoofed message tricked the trading software into updating the arbitrator's node address to one controlled by the attacker. By controlling this address, the attacker was able to position themselves as a participant in the multisig wallet creation process. This allowed them to construct a compromised multisig wallet, which they subsequently drained once the victim deposited their funds. The incident primarily impacted large-scale crypto-to-crypto offers, while fiat-based trading remained unaffected.
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
If you're auditing a protocol with similar architecture to RetoSwap, these are the critical security checks that could have prevented this incident (May 2026).
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The RetoSwap hack is one of many attacks that skilled auditors are trained to detect before deployment. Master real exploit patterns and defense techniques with hands-on Web3 security training.
The full story
This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.
