Arbitrary file read via external data path bypass

Path traversal in ONNX 1.15.0 and earlier allows remote attackers to read arbitrary local files through a crafted model. The external_data loader strips only leading slashes and periods before joining a tensor-supplied location to the base directory, so embedded traversal components escape that directory. Exploitation requires an application to load an attacker-controlled ONNX model, and disclosure is limited to files readable by that application.