Flaws in Passkey Implementation Show Old Attacks Still Work

July 22, 2026 · Dark Reading · Severity: HIGH

Researchers discovered exploitable flaws in Microsoft's passkey implementation ahead of the Black Hat security conference, demonstrating that even next-generation authentication mechanisms can contain critical vulnerabilities. Passkeys, which replace passwords with cryptographic key pairs stored on devices, are intended to be phishing-resistant and immune to credential theft, but implementation flaws in how they are generated, stored, validated, or synced between devices can reintroduce the very attack surfaces they aim to eliminate. The findings highlight that passkeys are only as secure as their implementation and that rushing to adopt new authentication standards without thorough security review can create unexpected weaknesses.