OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. In versions 2.1.0 and prior, a r

OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. In versions 2.1.0 and prior, a returning client's six-digit booking PIN can be brute-forced online in the victim tenant. A successful guess yields the client's booking access token, granting access to that client's appointment tunnel, which holds their end-to-end-encrypted appointment data, and the ability to act as the client, for example adding or cancelling appointments in the tunnel. The bypass is cross-tenant: state owned by one tenant removes an authentication protection of a different tenant. This crossing of the tenant boundary is the basis for the scope-changed vector. At time of publication, there are no publicly available patches.