The following was copied/pasted from No security update this month! - Pale Moon forum

Since there are no important security bugs to be fixed this month (yay!) as none of the Mozilla bugs actually apply to our code aside from a single, low risk defense-in-depth preventative patch (not an exposed vulnerability), we will be skipping the normally-scheduled 31.2.1 update and continue normal development for 31.3.0.

[ With Acknowledgement to Corrine Chorney, for posting at LandzDown. ]