Recently, applications powered by Large Language Models (LLMs) have made significant strides in tackling complex tasks. By harnessing the advanced reasoning capabilities and extensive knowledge embedded in LLMs, these applications can generate detailed action plans that are subsequently executed by external tools. Furthermore, the integration of retrieval-augmented generation (RAG) enhances performance by incorporating up-to-date, domain-specific knowledge into the planning and execution processes. This approach has seen widespread adoption across various sectors, including healthcare, finance, and software development. Meanwhile, there are also growing concerns regarding the security of LLM-based applications. Researchers have disclosed various attacks, represented by jailbreak and prompt injection, to hijack the output actions of these applications. Existing attacks mainly focus on crafting semantically harmful prompts, and their validity could diminish when security filters are employed. In this paper, we introduce AI$\mathbf{^2}$, a novel attack to manipulate the action plans of LLM-based applications. Different from existing solutions, the innovation of AI$\mathbf{^2}$ lies in leveraging the knowledge from the application's database to facilitate the construction of malicious but semantically-harmless prompts. To this end, it first collects action-aware knowledge from the victim application. Based on such knowledge, the attacker can generate misleading input, which can mislead the LLM to generate harmful action plans, while bypassing possible detection mechanisms easily. Our evaluations on three real-world applications demonstrate the effectiveness of AI$\mathbf{^2}$: it achieves an average attack success rate of 84.30\% with the best of 99.70\%. Besides, it gets an average bypass rate of 92.7\% against common safety filters and 59.45\% against dedicated defense.