A vulnerability exists in the fine-tuning lifecycle of Vision-Language Models (VLMs) derived from open-source base models, termed the "grey-box threat." Adversaries with white-box access to a public base model (e.g., Qwen2-VL) can generate universal adversarial images that successfully bypass safety guardrails in proprietary, fine-tuned downstream variants. This is achieved via the Simulated Ensemble Attack (SEA), which combines two techniques: Fine-tuning Trajectory Simulation (FTS), where…
Source: arXiv