In contemporary society, social networking websites has developed dramatically and became an indispensable component in our daily life. Since it can help create a more feature-rich online social community, third-party service has been widely adopted in online social networks (OSNs). Integrating these third-party sites and applications has not only extended business of both social network server and third party and but also promises to break down the garden walls of social-networking sites. While at the same time it dramatically raises concerns on privacy leakage. This article mainly focuses on the privacy disclosure issues caused by user’s behavior and third-party applications and websites. On the one hand, because of the diversity of usage behaviors, the revelation of personal information varies significantly. A survey is conducted to present empirical and quantitative result. On the other hand, the access mechanism between OSN and third party is not perfect enough. Besides, it could be a potential source of privacy leak that third-party services sometimes act as advertisers and information aggregators of a user's traversals. The relevant reasons and internal and external threats are presented. Finally, possible solutions to reduce the increasing information disclosure are provided. Actions should be taken along three fronts: the government, the users themselves as well as the third parties.