The most emerging communication medium for the last decade of years is Online Social Networks (OSNs). Online Social Network makes the communication quicker and cheaper. Facebook, Twitter, Google Plus, MySpace, Orkut, etc are the various existing online social networks. Among all the online social networks very few could turn the attention of the people towards them. However, all these social networks are available on the publicly accessible communication medium called internet. When these social networks are available in the internet, it will lead to various types of security issues. This paper discusses the various security related issues persists in online social networks.