A few weeks ago, Alex Kosowski (JSR 375 Specification Lead) gave a session at Devoxx Paris on the new Java EE Security API (JSR 375). During that session, Alex gave some background and the motivations that led to the creation of JSR 375. Alex then outlined some of the initial plans of the Expert Groups.
This session is particularly useful to understand what the EG is trying to accomplish, it will also provide sufficient background to start following the JSR 375 EG discussions (see here).
Note: The audio level is low at the beginning of the video but everything is fine around the 2m45 mark. Alex's slides can be found here.