Backdoor Attacks on Open Vocabulary Object Detectors via Multi-Modal Prompt Tuning
This addresses a critical security problem for high-stakes applications like robotics and autonomous driving, representing a novel attack surface rather than an incremental improvement.
The paper tackles the security risks of open-vocabulary object detectors by introducing the first backdoor attack study, revealing a vulnerability through prompt tuning, and proposes TrAP, a method that achieves high attack success rates for misclassification and object disappearance attacks while maintaining clean image performance.
Open-vocabulary object detectors (OVODs) unify vision and language to detect arbitrary object categories based on text prompts, enabling strong zero-shot generalization to novel concepts. As these models gain traction in high-stakes applications such as robotics, autonomous driving, and surveillance, understanding their security risks becomes crucial. In this work, we conduct the first study of backdoor attacks on OVODs and reveal a new attack surface introduced by prompt tuning. We propose TrAP (Trigger-Aware Prompt tuning), a multi-modal backdoor injection strategy that jointly optimizes prompt parameters in both image and text modalities along with visual triggers. TrAP enables the attacker to implant malicious behavior using lightweight, learnable prompt tokens without retraining the base model weights, thus preserving generalization while embedding a hidden backdoor. We adopt a curriculum-based training strategy that progressively shrinks the trigger size, enabling effective backdoor activation using small trigger patches at inference. Experiments across multiple datasets show that TrAP achieves high attack success rates for both object misclassification and object disappearance attacks, while also improving clean image performance on downstream datasets compared to the zero-shot setting.