This article develops an index to measure the level of susceptibility of courses to cheating using ChatGPT (Chat Generative Pre-trained Transformer), an advanced text-based artificial intelligence (AI) language model. It demonstrates the application of the index to a sample of business courses in a mid-sized university. The study finds that the vulnerability index varies across disciplines and teaching modalities. As advanced language models become more common in academic settings and create new educational challenges, the study provides an intuitive and practical mechanism for instructors and academic units to measure and assess the vulnerability of their courses to various language-based predictive models.