Abstract. [Context and motivation] In order to build successful software products and services, customer involvement and an understanding of customers' requirements and behaviours during the development process are essential. [Question/Problem] Although continuous deployment is gaining attention in the software industry as an approach for continuously learning from customers, there is no common overview of the topic yet. [Principal ideas/results] To provide a common overview, we conduct a secondary study that explores the state of reported evidence on customer input during continuous deployment in software engineering, including the potential benefits, challenges, methods and tools of the field. [Contribution] We report on a systematic literature review covering 25 primary studies. Our analysis of these studies reveals that although customer involvement in continuous deployment is highly relevant in the software industry today, it has been relatively unexplored in academic research. The field is seen as beneficial, but there are a number of challenges related to it, such as misperceptions among customers. In addition to providing a comprehensive overview of the research field, we clarify the gaps in knowledge that need to be studied further
