<p>Online social networks (OSNs) have transformed how users share personal information, yet they also pose significant privacy risks due to the vast accumulation of sensitive data. Protecting user privacy is critical, as data exposure can lead to identity theft, unauthorized access, and misuse. While OSN data is valuable for businesses, governments, and researchers, its release in original form raises privacy concerns, as conventional anonymization techniques struggle to address the demographic richness of these networks. This paper presents a comprehensive review of privacy challenges and anonymization strategies in OSNs. We analyze state-of-the-art privacy-preserving mechanisms, explore common privacy breaches, and assess classical anonymization techniques along with their limitations. The review identifies specific privacy risks, such as data harvesting, cyberbullying, targeted profiling, and social engineering attacks. It also examines attacker methodologies leveraging background knowledge to breach privacy. Our key contributions include highlighting challenges in anonymizing OSN data, reviewing advancements in privacy preservation, and identifying open issues requiring further research.</p>