ControlNet has enabled detailed spatial control in text-to-image diffusion models by incorporating additional visual conditions such as depth or edge maps. However, its effectiveness heavily depends on the availability of visual conditions that are precisely aligned with the generation goal specified by text prompt-a requirement that often fails in practice, especially for uncommon or imaginative scenes. For example, generating an image of a cat cooking in a specific pose may be infeasible due to the lack of suitable visual conditions. In contrast, structurally similar cues can often be found in more common settings-for instance, poses of humans cooking are widely available and can serve as rough visual guides. Unfortunately, existing ControlNet models struggle to use such loosely aligned visual conditions, often resulting in low text fidelity or visual artifacts. To address this limitation, we propose SemanticControl, a training-free method for effectively leveraging misaligned but semantically relevant visual conditions. Our approach adaptively suppresses the influence of the visual condition where it conflicts with the prompt, while strengthening guidance from the text. The key idea is to first run an auxiliary denoising process using a surrogate prompt aligned with the visual condition (e.g., "a human playing guitar" for a human pose condition) to extract informative attention masks, and then utilize these masks during the denoising of the actual target prompt (e.g., cat playing guitar). Experimental results demonstrate that our method improves performance under loosely aligned conditions across various conditions, including depth maps, edge maps, and human skeletons, outperforming existing baselines. Our code is available at https://mung3477.github.io/semantic-control.

In recent years, "prompt as a service" has greatly enhanced the utility of large language models (LLMs) by enabling them to perform various downstream tasks efficiently without fine-tuning. This has also increased the commercial value of prompts. However, the potential risk of leakage in these commercialized prompts remains largely underexplored. In this paper, we introduce a novel attack framework, PRSA, designed for prompt stealing attacks against LLMs. The main idea of PRSA is to infer the intent behind a prompt by analyzing its input-output content, enabling the generation of a surrogate prompt that replicates the original's functionality. Specifically, PRSA mainly consists of two key phases: prompt mutation and prompt pruning. In the mutation phase, we propose a prompt attention algorithm based on output difference. The algorithm facilitates the generation of effective surrogate prompts by learning key factors that influence the accurate inference of prompt intent. During the pruning phase, we employ a two-step related word identification strategy to detect and mask words that are highly related to the input, thus improving the generalizability of the surrogate prompts. We verify the actual threat of PRSA through evaluation in both real-world settings, non-interactive and interactive prompt services. The results strongly confirm the PRSA's effectiveness and generalizability. We have reported these findings to prompt service providers and actively collaborate with them to implement defensive measures.