This lecture explores the emerging challenge of undeclared AI-generated content in Wikipedia. As large language models such as ChatGPT trained on Wikipedia increasingly contribute content back to the platform, we face critical questions about information integrity. The session examines how this practice undermines Wikipedia's reliability and the various motivations that drive such contributions. Through real-world examples and technical analysis, we'll discuss detection methodologies and policy implications. The presentation aims to foster dialogue about necessary disclosure standards and verification methods to maintain Wikipedia's reliability as a knowledge source in an era where distinguishing between human and machine-written content becomes increasingly difficult.