Account takeover risk persists when attackers can exploit implementation gaps, browser incompatibilities, or alternate MFA paths to trigger a downgrade. In those cases, the attacker is not defeating FIDO directly. They are manipulating the user into a less secure flow, then intercepting credentials or session tokens through adversary-in-the-middle techniques.
Why Passkeys Reduce Password Theft but Do Not Eliminate Takeover Risk
FIDO-based passkeys remove a major class of phishing and credential replay attacks, but they do not make account takeover impossible. Risk remains when identity flows include fallback MFA, recovery channels, device binding gaps, or browser and platform edge cases that force users into weaker paths. The real issue is often not passkey cryptography itself, but the surrounding authentication architecture and session handling. Guidance in NIST SP 800-63 Digital Identity Guidelines reinforces that authenticators must be evaluated as part of the full identity lifecycle, not in isolation.
Security teams often assume that deploying passkeys closes the takeover problem, yet attackers usually target the seams: account recovery, help desk resets, SMS fallback, or token theft after initial sign-in. NHI Management Group’s Ultimate Guide to NHIs — Why NHI Security Matters Now shows how identity controls fail when governance is fragmented across systems and exceptions. In practice, many security teams encounter passkey bypasses only after a recovery abuse or session hijack has already occurred, rather than through intentional design review.
How Takeover Happens Around the Passkey Control
Passkeys are strongest when they remain the primary, non-bypassable authenticator and when the rest of the access path is equally hardened. Attackers rarely try to defeat the FIDO ceremony directly. They look for alternate routes that preserve the appearance of legitimate authentication while weakening the assurance level. That can include adversary-in-the-middle phishing against a fallback login, coercing the user into an email or SMS recovery path, stealing session cookies after authentication, or exploiting browser compatibility issues that trigger a non-passkey flow.
The practical defense is to treat the login journey as a chain of controls. Current best practice is evolving toward:
- Eliminating silent fallback to passwords where passkeys are enrolled.
- Hardening recovery with strong identity proofing and step-up checks.
- Binding sessions to device, context, or risk signals where feasible.
- Monitoring for new device enrollment, recovery changes, and abnormal token use.
- Reviewing whether the application honors phishing-resistant authentication everywhere, including mobile and legacy browsers.
That perspective aligns with the broader identity risk model described in Ultimate Guide to NHIs – Key Challenges and Risks, where excessive trust in a single control masks weak upstream and downstream processes. It also fits the control emphasis in NIST Cybersecurity Framework 2.0, which expects identity assurance, monitoring, and response to work together. These controls tend to break down in large enterprises with mixed device fleets and legacy apps because the weakest authentication path remains available somewhere in the estate.
Common Exceptions, Fallbacks, and High-Risk Edge Cases
Tighter authentication often increases user friction and support overhead, requiring organisations to balance phishing resistance against recovery complexity and business continuity. That tradeoff is real: passkeys can fail operationally if users lose devices, browse through incompatible clients, or rely on service desks that are pressured to bypass controls. The goal is not only stronger login technology, but fewer ungoverned exceptions.
There is no universal standard for this yet, but current guidance suggests three recurring edge cases deserve extra scrutiny. First, account recovery frequently becomes the soft underbelly, especially when reset links, knowledge-based checks, or email mailbox access can re-establish control. Second, session theft can still produce takeover even after a successful passkey login if token lifetime, device posture, or anomaly detection is weak. Third, organisations with consumer-facing or partner-facing apps often preserve fallback paths for compatibility, and those paths may remain more vulnerable than the passkey route itself.
This is why NHI Management Group continues to emphasize governance around the whole identity surface, not just the primary authenticator. The Top 10 NHI Issues resource shows how overlooked exceptions and stale controls create avoidable exposure across identity systems. For risk teams, the operational lesson is simple: passkeys should be measured by how completely they remove weaker alternatives, not by enrollment numbers alone.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10 and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST SP 800-63, NIST CSF 2.0 and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-63 | Defines authenticators, recovery, and assurance across the full identity lifecycle. | |
| NIST CSF 2.0 | PR.AA | Identity management and authentication are central to preventing account takeover. |
| OWASP Agentic AI Top 10 | Phishing-resistant auth still fails if attackers redirect users into weaker flows. | |
| NIST AI RMF | Risk management must account for authentication exceptions and session abuse. | |
| OWASP Non-Human Identity Top 10 | NHI-06 | Controls around credential handling and fallback paths mirror NHI takeover patterns. |
Review all fallback and recovery paths against NIST identity assurance guidance before treating passkeys as sufficient.
