© 2020 IEEE.The use of online social networks is one of daily activity for people. OSNs' users share contents which sometimes has other users' information on. This type of data sharing is called co-owned data sharing and it is one of the most popular reasons for privacy leakages in OSNs platforms. OSNs' users claim that the responsibility of preserving users' privacy should be taken by those platforms. To do so, there are different approaches taken by OSNs for protecting users' privacy and providing the most secure environment to their users. This study proposes a model which should be adopted by OSNs platforms for a more secure environment. The model is developed on top of a hypothesis, the proof of the hypothesis is done with analysis on two questionnaires. Results of the analysis show that group decision making and reputation systems are needed to have more secure online social network platforms.