Pass-the-Passkey: What Michael Grafnetter's Black Hat Research Means for Entra Admins

Passkeys are phishing-resistant. But that resistance is enforced by your browser, which binds every authentication to the origin that requested it. Skip the browser, and the guarantee weakens.In this episode of Entra.Chat, I spoke with Michael Grafnetter, Principal Security Researcher at SpecterOps and Microsoft MVP, about the Pass-the-Passkey research he presented at Black Hat USA 2026. A family of attacks against passkey implementations across Windows, Microsoft Entra ID, browsers and password managers.Michael starts with the vulnerability chain he reported to Microsoft. Windows was writing the complete passkey assertion into the event log, and Microsoft Entra ID would accept a replay of that assertion for up to ten minutes. Any user able to read those logs including a member of Remote Desktop Users on a shared server, or unprivileged malware quietly reading event logs without tripping EDR could impersonate whoever had just signed in. If that person was a Global Administrator, so was the attacker. Windows now truncates the logged message, and Microsoft Entra ID checks authenticator signature counters to reject replays.One clarification Michael is emphatic about: private keys were never written to the event log. They stay bound to the TPM or never leave the security key at all. What leaked were the short-lived digital signatures made by those keys and for this attack, that was enough.We also covered the attacks that do not depend on any single bug. Malware running without administrator rights can call the native Windows WebAuthn APIs directly and raise a passkey prompt flood that keeps returning until the user gives in and approves it. Synced passkeys, exported from a password manager and decrypted with a keylogged password, hand an attacker a credential with no ten-minute limit at all. And a browser-hooking technique Michael calls a passkey detour attack quietly redirects a legitimate assertion into the attacker’s own session.The defensive thread running through all of it is the same: every one of these attacks assumes malware is already on the device. That makes device trust the key control. Privileged access workstations for administrators, Conditional Access requiring compliant devices with EDR running, and the clean source principle that says a system can only be as trustworthy as whatever it depends on.Michael closes on an optimistic note, and it is worth repeating. Passkeys are still the future. They remain far better than passwords and phishable MFA, and every attack here costs an adversary vastly more effort than sending a phishing link. But as passkeys become the default in Microsoft Entra, the threat model deserves an honest read.Watch the demos. This episode includes three on-screen demonstrations that are much easier to follow on video than on audio.This episode brought to you by Workplace Ninjas USWorkplace Ninjas US isn’t just another tech conference. It’s where Microsoft experts, MVPs, engineers, and IT professionals come together to learn, network, and build lasting connections. We are a community built on diversity, mentoring, fellowship, and creating a place where everyone belongs.Our core DNA comes down to a few pillars:* Over 60 sessions from the largest collection of MVPs and SMEs you will find in any event in America.* Amazing mentoring, development, and growth through our one on one mentoring system with any speaker, our hackathon, community theatre and more.* A diverse expo hall featuring some of the best Microsoft partners in the world that will help you drive deep efficiencies from your M365 stack.* A place where you will learn how to think differently and collaborate better through a collection of activities and can return refreshed and invigorated to drive change in your organization.* Don’t miss out on our early bird tickets while supplies lastSubscribe with your favorite podcast player or watch on YouTube About Michael GrafnetterMichael Grafnetter is a Principal Security Researcher at SpecterOps and a Microsoft MVP, based in Prague. He specializes in Microsoft Entra ID and Active Directory security and PowerShell. He is the author of the DSInternals PowerShell module and the researcher who originally discovered the Shadow Credentials attack technique, now widely used by penetration testers, red teamers and attackers alike. He has presented his security research at international conferences including Black Hat Europe, Black Hat USA, SecTor, TROOPERS and BSides Lisbon.* LinkedIn - https://www.linkedin.com/in/grafnetter/Related Links* Pass-the-Passkey research and tools, including Passkey Injector and the DSInternals.Passkeys module (discussed at 14:57 and 34:22) - https://github.com/SpecterOps/pass-the-passkey* Pass-the-Passkey research paper from Black Hat USA 2026 (introduced at 07:34) - https://specterops.io/wp-content/uploads/sites/3/2026/08/Pass-the-Passkey_A4_v2.pdf* Shadow Credentials, Michael’s earlier Active Directory research (mentioned at 01:46) - https://specterops.io/blog/2021/06/17/shadow-credentials-abusing-key-trust-account-mapping-for-account-takeover/* DSInternals PowerShell module (mentioned at 01:34) - https://www.dsinternals.com/en/* Passkeys (FIDO2) authentication in Microsoft Entra ID (context throughout) - https://learn.microsoft.com/entra/identity/authentication/concept-authentication-passkeys-fido2* Synced passkeys, device-bound passkeys and passkey profiles (discussed at 23:21) - https://learn.microsoft.com/entra/identity/authentication/how-to-authentication-passkeys-fido2* Deploy phishing-resistant passwordless authentication (context at 18:08) - https://learn.microsoft.com/entra/identity/authentication/how-to-deploy-phishing-resistant-passwordless-authentication* Require device compliance with Conditional Access (recommended at 21:12) - https://learn.microsoft.com/entra/identity/conditional-access/policy-all-users-device-compliance* Privileged access devices and the clean source principle (discussed at 21:55 and 35:41) - https://learn.microsoft.com/security/privileged-access-workstations/privileged-access-devices* Unit 42, “Pass the Passkey: A Novel Attack Surface in Passwordless Authentication” — the Palo Alto research on Google Password Manager passkeys (mentioned at 26:27) - https://unit42.paloaltonetworks.com/passwordless-authentication-security-risks/Related Entra.Chat Episodes* From SMS MFA to Passkeys: A Practical Microsoft Entra Migration Plan - https://entra.news/p/from-sms-mfa-to-passkeys-a-practical* 5 Lessons from Rolling Out Passkeys to Millions of Users - https://entra.news/p/5-lessons-from-rolling-out-passkeys* Attackers Are Targeting The AI Ecosystem You Cannot See - https://entra.news/p/attackers-are-targeting-the-ai-ecosystemChapters00:00 Intro01:02 Meet Michael Grafnetter03:09 How the Research Started06:50 Windows Hello for Business Was the First Passkey07:30 The Signature in Your Event Log10:18 No, Private Keys Are Not Logged12:25 How Entra Mitigated the Replay13:44 Demo: Signing In With a Stolen Signature15:22 Malware-Initiated Passkey Phishing18:08 The Browser Is What Makes Passkeys Phishing-Resistant20:42 What Defenders Should Actually Do23:04 Synced Passkeys and the Export Problem26:13 Credential Exchange and Password Manager Risk28:19 The Passkey Detour Attack30:43 The Authentication Broker Debate31:57 RDP Redirection and Remote Passkey Abuse32:59 Spotting a Suspicious Passkey Prompt34:46 Passkeys Are Still the FuturePodcast AppsApple Podcast - https://entra.chat/appleYouTube - https://entra.chat/youtubeSpotify - https://entra.chat/spotifyOvercast - https://entra.chat/overcastPocketcast - https://entra.chat/pocketcastOthers - https://entra.chat/rssMerill’s socialsYouTube - youtube.com/@merillxLinkedIn - linkedin.com/in/merillTwitter - twitter.com/merillTikTok - tiktok.com/@merillfBluesky - bsky.app/profile/merill.netMastodon - infosec.exchange/@merillThreads - threads.net/@merillfGitHub - github.com/merill Get full access to Entra.News - Your weekly dose of Microsoft Entra at entra.news/subscribe