Training jobs load pickled checkpoints from an external mirror
A fine-tuning pipeline pulled a base checkpoint from an unpinned external mirror and loaded it with a format that can execute code. Our benign test artifact ran and called back from inside the training environment.
- Reproduction
- Publish test artifact ███ to the mirror the pipeline trusts.
- Trigger the scheduled fine-tuning job.
- Observe the callback from the training network.
- Impact
- Anyone able to publish to the mirror could run code next to training data and credentials.
- Control
- Weights-only formats, hash-pinned artifacts and loading inside a network-isolated job.
- Retest
- The test artifact was rejected at hash verification. A pinned clean checkpoint trained normally.