Charles Guillemet, CTO of hardware wallet maker Ledger, announced the fix for a vulnerability affecting clear signing in its Ethereum app.

The bug was discovered by the Ledger Donjon team using an AI-powered vulnerability detection system, according to a senior executive. The issue affected the clear signing feature, which displays transaction details—the amount, address, and smart contract actions—on-screen before the user confirms them.

Ledger deployed the patch approximately two weeks before it was publicly disclosed. The developers assured that users with up-to-date firmware and app versions are protected. As of August 24, there were no confirmed thefts related to this vulnerability.

TestMachine researchers, using the AI tool Azimuth, reported that hackers could replace transaction data and send a competing command while a Ledger user was still viewing the original transaction. As a result, the device could display one transaction while signing another. TestMachine stated that the vulnerability affects several hardware wallet models, including the Nano X, Nano S Plus, Stax, and Apex.

Ledger itself has not published a detailed technical description of the vulnerability or a list of affected wallet versions. Ledger's CTO said TestMachine contacted Ledger after the company released a fix. He called TestMachine's claim of the issue "scaremongering for attention."

TestMachine analysts stated that they shared their research findings with Ledger and waived a reward.

Ledger representatives recommended wallet owners update their Ledger Wallet software, device firmware, and the installed Ethereum app. Furthermore, updating the desktop or mobile interface alone may not be sufficient for an outdated device app. Users should verify transaction details directly on the device's secure screen. Blind signing can be dangerous, as the device may not always be able to display every smart contract action in a readable format, Ledger specialists complained.

Previously, anonymous blockchain researcher ZachXBT suggested subscribers stop using Ledger hardware wallets. The blockchain sleuth fears that too frequent updates alter the interface and sometimes disrupt the device's basic functionality.

Ledger developers discovered a vulnerability in wallet signatures.