Malware on a Windows PC can copy every passkey that Chrome saved to your Google account. Palo Alto Networks' Unit 42 team found three ways to attack Google's synced passkeys. The mildest attack logs an attacker in with no fingerprint, no PIN, and nothing on your screen, at any site that never checks that a person was there.
They tested Chrome with Google Password Manager on Windows PCs with TPM 2.0, which Windows 11 requires. All three need malware already on the machine, and none break the math that makes passkeys hard to steal.
Signing in without your finger
The first attack lets malware get a login approval out of Google in your name, using the key that Chrome keeps on the machine.
That approval carries a marker saying whether a fingerprint or PIN was really checked. GitHub demands the check, throws out approvals that are missing the marker, and stops the attack. In Unit 42's test eBay asked for the check but did not properly read the marker, so the login went through. eBay has since fixed that.
Unit 42's passkey attack research
Teaching Google to trust the attacker
The second attack goes further. Malware deletes the local file holding the passkey setup. The next time you use a passkey, Chrome starts setting the device up again, and in that window the attacker registers their own key. Unit 42 says Google's servers do not check whether that key came from real hardware, and the report does not say whether that changed.
Google then treats anything signed with the attacker's key as proof you unlocked your device with a fingerprint or PIN. The attacker signs in from their own computer and never touches yours. But it is not silent. Setting the device up again makes Chrome ask for your Google Password Manager recovery PIN, a prompt you should rarely see.
What the passkey disclosure leaves unresolved
One master key for everything
The third attack takes every passkey at once. One master key encrypts every passkey synced to a Google account, and Chrome gets handed it during that setup. So the attacker forces that setup and dumps the browser's memory while the key is briefly there. The same PIN prompt is the warning here too.
Unit 42 first found the key in plain text in Chrome's own logs. Google took it out after the report, but the key still reaches the browser. Unit 42 says Google has no way to rotate or cancel it, so every passkey you add later is guarded by the secret the attacker already holds. The fix, Unit 42 says, is for Google to stop handing it to the browser at all.
Unit 42 on the master key that cannot be rotated
Passkeys are still far harder to phish than passwords. A fake login page cannot trick one out of you, and Google's own documentation says a passkey cannot be shared or copied. Unit 42 showed that malware already on the machine can get around that.
Unit 42's report lists no CVE, and The Hacker News found no match in the national vulnerability database on August 3. The Hacker News asked Google whether changing that PIN cancels a stolen master key, with no answer by publication.
