ZAC is an open-source, workflow-based Common Ground component for Dutch municipal case management. Prior to 5.2.0, by-id read endpoints in "src/main/kotlin/nl/info/zac/app/zaak/ZaakRestService.kt" omit "assertPolicy"("policyService.readZaakRechten(zaak).lezen") authorization. "RequestAuthorizationFilter" and "hasAnyApplicationRole" require only an application role on any zaaktype, not the target case's type, while "zaak-rechten.rego" enforces the actual "zaaktype_allowed" boundary only when invoked. An authenticated low-privileged municipal user who knows a case or decision UUID can use "GET /rest/zaken/besluit/zaakUuid/{uuid}" ("listBesluitenForZaakUUID") to read decisions including types, dates, and free-text toelichting; "GET /rest/zaken/besluit/{uuid}/historie" ("listBesluitHistorie") to read audit old/new values; and "GET /rest/zaken/{uuid}/process-diagram" ("downloadProcessDiagram") to read BPMN workflow state across unauthorized zaaktypes. The advisory also identifies "zaak/{uuid}/afzender" ("listAfzendersVoorZaak") as exposing zaaktype mailbox configuration without a policy check. The search/_zoek path is correctly authorization-filtered and is not part of this by-id read cluster. This issue is fixed in version 5.2.0.