I. Introduction
Online social networks (OSNs) contain sensitive user information. Leaking the private information of users, e.g., users’ interests, users’ profiles, and the linking relationships between users, can cause great panic to OSN users and service providers. In one example, Cambridge Analytica gained access to approximately 87 million Facebook accounts. In 2018, following the data scandal, Facebook apologized amid public outcry and fallen stock prices [24].