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Briefing

A sophisticated phishing attack leveraging Ethereum’s “Permit” signature feature resulted in a $6.28 million loss for a crypto whale on September 18, 2025. This incident highlights a critical vulnerability where legitimate off-chain approval mechanisms are misused to bypass traditional security checks, allowing attackers to drain staked Ethereum (stETH) and Aave-wrapped Bitcoin (aEthWBTC) without gas fees. The attack underscores the escalating threat of EIP-7702 batch-signature scams and direct malicious contract transfers, contributing to August 2025’s $12.17 million in phishing-related losses.

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Context

Prior to this incident, the digital asset landscape has seen a concerning surge in phishing attacks, with August 2025 alone registering a 72% monthly increase in losses to $12.17 million across over 15,230 victims. The prevailing attack surface includes sophisticated social engineering tactics and the exploitation of legitimate, yet often misunderstood, smart contract functionalities designed for convenience, such as token approval mechanisms. The absence of gas fees in such off-chain approvals has historically masked malicious intent, rendering users susceptible to seemingly innocuous prompts.

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Analysis

The attack leveraged the “Permit” signature feature, intended to streamline token approvals, by disguising malicious activity as a routine wallet confirmation. The attacker combined the Permit signature with the TransferFrom function, enabling the direct draining of assets. Crucially, because the approval occurs off-chain, the transaction did not require gas fees, effectively bypassing a key indicator of on-chain activity and leaving the victim unaware until the funds were already transferred. This method allows for a cost-effective and stealthy exploitation of user permissions, circumventing complex on-chain hacks and high gas strategies.

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Parameters

  • Protocol TargetedEthereum Ecosystem (via Permit feature misuse)
  • Attack VectorPhishing via Malicious Permit Signature
  • Financial Impact ∞ $6.28 Million
  • Assets LostStaked Ethereum (stETH), Aave-wrapped Bitcoin (aEthWBTC)
  • Date of Incident ∞ September 18, 2025
  • Affected Entity ∞ Crypto Whale
  • Detection Firm ∞ Scam Sniffer

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Outlook

Users must adopt a more stringent security posture by meticulously scrutinizing all wallet confirmation requests and avoiding the granting of unlimited token permissions. Immediate mitigation steps include regularly reviewing and revoking token approvals on relevant protocols and securing significant holdings with hardware wallets. This incident will likely drive a push for enhanced user education on signature types and the development of more robust wallet interfaces that clearly differentiate between various approval mechanisms, potentially establishing new best practices for off-chain transaction security.

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Verdict

The escalating misuse of legitimate protocol features like Ethereum’s Permit for sophisticated phishing attacks represents a critical and evolving threat that demands immediate, proactive user vigilance and enhanced platform-level safeguards.

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off-chain approval

Definition ∞ Off-chain approval signifies a process where authorization for a transaction or action is granted outside of the main blockchain ledger, often to improve efficiency and reduce costs.

phishing attacks

Definition ∞ Phishing attacks are fraudulent attempts to obtain sensitive information, such as usernames, passwords, and credit card details, by disguising as a trustworthy entity in electronic communication.

permit signature

Definition ∞ A permit signature is an off-chain cryptographic signature that authorizes a third party to spend a user's ERC-20 tokens without requiring an on-chain approval transaction.

ethereum ecosystem

Definition ∞ The Ethereum ecosystem comprises the network of decentralized applications, smart contracts, developers, users, and infrastructure built upon the Ethereum blockchain.

phishing

Definition ∞ Phishing, in the digital asset space, involves deceptive practices aimed at tricking individuals into divulging sensitive information, such as private keys or login credentials, typically through fraudulent communications.

staked ethereum

Definition ∞ Staked Ethereum refers to Ether (ETH) tokens that are locked up in the Ethereum network's proof-of-stake consensus mechanism to secure the blockchain.

token approvals

Definition ∞ Token approvals are permissions granted by a token holder that allow a smart contract or another address to interact with their tokens, such as transferring or spending them.

ethereum

Definition ∞ Ethereum is a decentralized, open-source blockchain system that facilitates the creation and execution of smart contracts and decentralized applications (dApps).