Users’ personal data is collected by various third-party services on modern websites. Often this happens without the users’ knowledge, creating serious privacy risks especially when sensitive information such as health or political data is being processed. This paper studies how website maintainers respond to disclosures of third-party data leaks in their web services. We conduct a longitudinal comparison with two time points for four different categories of Finnish websites – online pharmacies, healthcare service websites, municipal websites, and voting advice applications. The maintainers of these websites were informed about third-party data leaks on their websites. The findings show how effectively website maintainers reacted to these disclosures in different scenarios and how the data leak situation evolved over time. These results illustrate real-world data-leak prevention practices and their effectiveness in different kinds of sensitive web services.