ArcadeDB before 26.7.2 fails to enforce the UPDATE_SCHEMA database permission on the ALTER TYPE ... CUSTOM and ALTER TYPE ... BUCKETSELECTIONSTRATEGY SQL operations, which map to setCustomValue and setBucketSelectionStrategy in LocalDocumentType. An authenticated user with only read access (e.g., a read-only API token) can submit these ALTER TYPE statements via the HTTP command endpoint to mutate a type's custom schema metadata and bucket-selection strategy, bypassing the documented updateSchema permission boundary and potentially corrupting schema metadata and record routing.