analysis of prompt injection, which is identified as the leading security vulnerability in applications powered by Large Language Models (LLMs). It explains that this threat arises from the inherent architecture of LLMs, which struggle to differentiate between trusted developer instructions and untrusted user input. The text categorizes prompt injection into direct and indirect attacks, detailing various techniques for each, such as jailbreaking and data exfiltration via hidden payloads in external data. Furthermore, it outlines a multi-layered, defense-in-depth strategy for detection and prevention, emphasizing the importance of secure prompt engineering, architectural safeguards like the principle of least privilege, and continuous operational security. The source concludes by stressing that no single solution exists and that a holistic approach is crucial to securing evolving agentic and multimodal AI systems.