How should security teams use passkeys and WebAuthn in browser extensions without weakening access controls?

Security teams should treat passkeys and WebAuthn as stronger authentication, not as a replacement for policy. Use them with phishing resistant MFA, device trust checks, session timeout controls, and recovery processes that do not create weaker fallback paths. The goal is to reduce credential replay risk while preserving usable access across approved browsers and devices.

Why This Matters for Security Teams

Passkeys and WebAuthn improve phishing resistance, but browser extensions sit in a different risk class than ordinary web logins. Extensions can broaden the attack surface through injected scripts, token exposure, over-broad permissions, and session abuse, so the control question is not “is authentication strong?” but “does the extension preserve the same access policy and device trust boundaries as the browser?” Guidance in OWASP Non-Human Identity Top 10 and NIST identity guidance both point toward stronger proof of identity, but neither treats authentication strength as sufficient on its own.

This matters because browser extensions often become a convenience layer that silently weakens session governance: long-lived logins, broad scopes, weak recovery flows, and inconsistent device checks. In NHI terms, the extension can become a privileged execution environment that must be governed like any other identity-bearing workload. NHI Management Group research shows how quickly weak governance turns into exposure, with the Ultimate Guide to NHIs reporting that 96% of organisations store secrets outside secrets managers in vulnerable locations. In practice, many security teams discover extension-driven access drift only after a session, token, or recovery path has already been abused.

How It Works in Practice

Security teams should treat WebAuthn as the authentication ceremony, then layer policy around the session that the browser extension receives. That means using passkeys for phishing-resistant sign-in, but still enforcing device trust, conditional access, and session expiry before the extension can perform sensitive actions. The stronger pattern is to bind access to the authenticated user, the enrolled device, and the approved browser context, rather than granting the extension a permanent “trusted” state.

In operational terms, the extension should request only the minimum scope needed for the task, with short-lived session tokens and explicit re-authentication for risky actions. Where possible, tie access to controls described in NIST SP 800-53 Rev 5 Security and Privacy Controls, especially least privilege, session management, and access enforcement. For identity assurance, NIST SP 800-63 Digital Identity Guidelines support the idea that authenticators do not replace the need for lifecycle and recovery controls.

• Use passkeys for primary authentication, not as a bypass for policy decisions.
• Require device posture or managed-browser checks before the extension receives usable session access.
• Issue short-lived tokens and revoke them when the browser context changes or the session times out.
• Separate recovery from day-to-day access so fallback does not become a weaker permanent path.
• Review extension permissions as rigorously as privileged application scopes.

This approach aligns with NHI thinking as well, because an extension that can call APIs or move data behaves like an identity-bearing workload. The Ultimate Guide to NHIs — Key Challenges and Risks shows why over-privilege and weak rotation matter across identity types, not just service accounts. These controls tend to break down when extensions must operate across unmanaged browsers and bring-your-own-device environments because device trust cannot be enforced consistently.

Common Variations and Edge Cases

Tighter passkey and WebAuthn policy often increases support burden, requiring organisations to balance phishing resistance against user recovery friction. That tradeoff is real, especially for shared workstations, contractor access, and environments where browser extensions must survive frequent profile resets. Current guidance suggests that exceptions should be explicit, temporary, and heavily monitored, not silently embedded in default access paths.

One common edge case is recovery after passkey loss. If the fallback is a weaker password reset or broad help-desk override, the overall control strength drops to the weakest path. Another is extension synchronization across devices, where a user signs in with a strong passkey on one device but the extension inherits access on another device that was never evaluated. Security teams should require re-verification on device change and avoid assuming the browser extension itself is an adequate trust anchor.

For teams governing higher-risk access, OWASP Non-Human Identity Top 10 and the NHI research above reinforce the same operational lesson: authentication strength must be matched by lifecycle control. The safest pattern is a short-lived, context-aware session with clear expiry, revocation, and recovery rules. That guidance is still evolving for browser extensions, so policy should be tested against real failure modes rather than assumed safe by default.

Related resources from NHI Mgmt Group

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• How should security teams govern access requests in ServiceNow without weakening IAM controls?