Security researchers have uncovered three attack techniques that could allow malware on compromised Windows computers to abuse passkeys synchronized through Google Password Manager. The attacks, collectively called “Pass-ta-key,” target Chrome devices equipped with a Trusted Platform Module (TPM). Rather than breaking the cryptography behind passkeys, the techniques exploit weaknesses in device registration, recovery, user verification, and cloud synchronization.
Passkeys are widely considered safer than passwords because they cannot be guessed, reused, or easily stolen through phishing. They normally rely on a device-based cryptographic key and may require a PIN, fingerprint, or facial recognition to approve a login. However, Unit 42 researchers found that malware already running on a victim’s computer could manipulate Chrome’s trusted-device mechanisms without requiring administrator privileges or direct user interaction.
The first technique, Pass-ta-key, abuses Chrome’s TPM-backed device identity key to make Google’s cloud authenticator believe that a request came from the legitimate computer. The service may then return a valid authentication assertion that attackers can use to access a protected account, even without biometric or PIN verification. This attack failed against GitHub because the platform correctly checked the WebAuthn user-verification flag, but it succeeded against eBay before the company fixed the validation issue.
The second method, Silver Pass-ta-key, enables attackers to register their own verification key during a forced Chrome re-registration process. Malware can invalidate the existing verification state or delete local passkey-related data, allowing the attacker-controlled key to be accepted as proof that the device was unlocked by its owner. The most serious technique, Golden Pass-ta-key, attempts to extract Google Password Manager’s Security Domain Secret from Chrome’s memory. This master key encrypts synchronized passkey records, so stealing it could allow attackers to recover private keys and impersonate the victim from another device.
Unit 42 said the stolen secret could potentially decrypt both existing and future passkeys because Google’s current implementation reportedly does not provide a method to rotate or revoke it. The findings highlight that passkeys remain resistant to phishing but cannot fully protect accounts when malware controls a trusted device or browser process. Websites should strictly validate user-verification signals, while credential managers should strengthen device enrollment, recovery, re-registration, and protection of encryption keys in memory. Google was notified of the research, although a complete public response or confirmation of remediation was not immediately available.
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