IBM DataStage on Cloud Pak for Data: insecure direct object reference

IBM DataStage on Cloud Pak for Data 5.4.0.0 concatenates three caller-supplied strings into a String.format path on the shared /ds-storage RWX PVC and returns the file with no project ACL — pure IDOR plus traversal. Read is constrained to files named job.log/error.log, but DataStage job logs routinely carry connection strings, {dsnextenc} ciphertexts (decryptable via d2-f023), and customer-data row samples. This is the operator's tenant-to-tenant PVC-leakage threat verbatim; MEDIUM→HIGH via threat match.