When signing up for new mobile apps, users are often provided the option of using their Facebook or other social media credentials (i.e., single sign-on services; SSO). While SSO is designed to make the login process more seamless and convenient, recent social media data breaches may give pause to users by raising security concerns about their online transactions. In particular, users logging into sensitive services, such as dating apps, may feel hesitant to adopt SSO due to perceived potential data leakage to their social networks. We tested this proposition through a user study (N = 364) and found that individual differences in online security perceptions predict the use of SSO for certain sensitive services (e.g., affair apps), but not others (e.g., matchmaking apps). Informed by theory, potential mediators of this relationship (perceived security, ease of sharing, and usability) were also explored, thus shedding light on psychologically salient drivers of SSO adoption.