$5.87M Drained in Minutes: How a Public Function Let an Attacker Register as a "Legitimate Signer"

smart contractapproval exploitDeFi securityCertiKwallet securityrevoke approvalcrypto asset protection

Not a Hack—A Design Flaw Legally Exploited

On May 7, 2026, CertiK issued an urgent security alert: approximately $5.87 million in pre-authorized funds had been stolen through contract address 0xeEeEEe53033F7227d488ae83a27Bc9A9D5051756.

The core of this attack was not a complex exploit—it was a design flaw. The contract contained a publicly callable function that allowed anyone to register themselves as an "AllowedOrderSigner." The attacker used this mechanism to self-register as a legitimate signer, then executed orders to directly transfer pre-approved funds from victim addresses.

The Hidden Risk of Pre-Authorization: You Approved More Than You Realized

This attack once again exposes a systemic risk within the DeFi ecosystem's approval mechanism. When a user grants a contract ERC-20 token transfer permissions, that approval typically remains active indefinitely until explicitly revoked. If the contract itself contains a logic flaw or is maliciously exploited, attackers can legally transfer assets through contract calls without ever obtaining the user's private key.

In this incident, the root cause of victim losses was not a compromised wallet—it was a pre-existing approval granted to a flawed contract that was never cleaned up.

Act Now: Revoking Approvals Is the Most Urgent Step

CertiK has explicitly warned all users who have interacted with this contract: immediately revoke all approvals to the vulnerable contract to prevent further asset loss. Users can check and batch-revoke existing approvals through tools such as revoke.cash.

For DeFi platforms and compliance teams, approval-abuse attacks typically exhibit identifiable on-chain patterns. Trustformer KYT monitors abnormal approval calls and batch transfer behavior in real time, helping platforms issue risk alerts before assets are drained at scale and keeping losses to a minimum.

About Trustformer

Trustformer is a leading blockchain security and compliance technology company specializing in providing professional risk management and compliance solutions for the global cryptocurrency ecosystem. We have developed the cutting-edge Trustformer KYT (Know Your Transaction) platform, which integrates artificial intelligence, blockchain analytics, and regulatory technology to deliver comprehensive, accurate real-time transaction monitoring, risk assessment, and suspicious activity reporting services.

With deep industry expertise and technological innovation, Trustformer is dedicated to helping Virtual Asset Service Providers (VASPs), crypto financial institutions, and investors build a safer and more transparent crypto financial environment. We believe that driving compliance and trust through technology can contribute to the thriving growth of the global digital economy.