Google Password Manager Attacks Could Let Malware Hijack Passkey-Protected Accounts

Unit 42 (Palo Alto Networks) detailed three post-compromise attack paths against Chrome's Google Password Manager cloud authenticator, collectively named 'Pass-ta-key', 'Silver Pass-ta-key', and 'Golden Pass-ta-key'. All attacks require malware already running on the victim's Windows machine with TPM present, and none break passkey cryptography directly — instead they exploit weaknesses in the surrounding implementation.

1. **Pass-ta-key**: Malware extracts Chrome's wrapped TPM device identity key blob from local storage (%LocalAppData%\Google\Chrome\User Data\<Profile>\Sync Data\LevelDB) and uses Windows CNG (NCryptSignHash) API calls to sign attacker-controlled requests without any user interaction. The TPM key is created without a key name (preventing persistence), exported as an opaque blob, and reloaded under a flag suppressing prompts. The resulting assertion lacks the User Verified (UV) flag. Sites enforcing userVerification=required (e.g., GitHub) reject it, but those that don't (e.g., eBay, prior to fix) accepted it.

2. **Silver Pass-ta-key**: Malware forces Chrome device re-enrollment, then registers an attacker-controlled user-verification key during the window before Chrome creates its own UV key (deferred_uv_key_creation state confirmed in Chromium source). Assertions signed with this key carry the UV flag, enabling persistent logins from the attacker's environment without the victim's device. The service reportedly does not verify hardware attestation for newly registered keys.

3. **Golden Pass-ta-key**: Malware triggers re-enrollment, then reads the 32-byte Security Domain Secret (SDS) from Chrome's process memory while it briefly exists in plaintext. The SDS can decrypt all synced passkey private keys, enabling account takeover and persistence. Google reportedly removed an earlier SDS exposure from Chrome's FIDO logs, but the secret still enters Chrome process memory. No CVE identifiers were assigned, and no exploits in the wild were reported as of August 3, 2026.