A user signs on to a cloud-based social media platform. In another browser tab, the user finds an article worth posting to the social media platform. The user clicks on the platform's icon listed on…

Single sign-on (SSO) allows a user to log in once and access multiple related applications without re-authenticating, but the example describes interaction between a website and a social media platform, implying a broader trust relationship beyond just login.

Insecure direct identifiers relate to vulnerabilities where predictable identifiers can be exploited to access resources, which is unrelated to the described user experience.

This scenario exemplifies identity federation, where the social media platform acts as an Identity Provider (IdP) and the article's website acts as a Relying Party (RP). The user's existing authentication session with the IdP (social media platform) allows the RP to perform an action (posting the article) on behalf of the user, leveraging the established trust relationship and shared identity information.

Cross-site scripting (XSS) is a type of web security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users, which is not what is happening in this secure-by-design interaction.