This paper proposes the first Source-Aware Membership Audit (SMA) methodology that precisely identifies the source of content generated from Retrieval-Augmented Generation (RAG) and Multimodal Retrieval-Augmented Generation (MRAG). To overcome the limitations of existing membership inference methods, which cannot accurately identify the sources (transfer learning data, external search results, and user input) of generated content due to the complexity of RAG/MRAG systems, we utilize a zero-order optimization-based attribute estimation mechanism and cross-modal attribute techniques. Specifically, we utilize MLLM to convert image inputs into text, enabling membership inference on image search history in MRAG systems. This presents a novel perspective that focuses on "where content comes from," rather than whether data is "remembered."