OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. Prior to 1.1.1, POST /api/auth/passkeys accepts a request-body userId and attacker-supplied passkey without an authenticated session, does not call WebAuthnService.verifyRegistration, and does not bind enrollment to locals.user.id. An unauthenticated attacker who knows the public tenant ID and the target staff email can use the public booking bootstrap and GET /api/tenants/[id]/appointments/staff-public-keys to obtain candidate userId values. The attacker first causes UserService.addAdditionalPasskey to store a controlled public key for a candidate userId, then attempts login with the target email; the login check compares verificationResult.userId with the email-resolved account and reveals whether the injected credential belongs to that target. Repeating this injection-before-login sequence identifies the matching userId, and the normal login endpoint accepts the attacker's assertion for the stored key and creates a STAFF session. The session can expose tenant data and reveal TENANT_ADMIN identifiers for further takeover; GLOBAL_ADMIN accounts are not reachable through this tenant-scoped path. A hijacked TENANT_ADMIN can modify or delete tenant resources and key shares, potentially making appointment data permanently undecryptable and taking booking services offline. This issue is fixed in version 1.1.1.