Selecting an external links redirects the user to content hosted outside of Fluid Topics.
The topic open in the Reader page (SSO Realms) belongs to the Fluid Topics Integration Guide. It contains a link that redirects the user to a Wikipedia page with information about the SSO authentication scheme:
Navigation tip for external links
If the user left-clicks when selecting an external link, it opens in the same tab of the same browser window. By right-clicking, it is possible to open the link in a new tab or browser window.