See Maxlength - Moderately critical - Cross Site Scripting - SA-CONTRIB-2019-073.
This release fixes access issue of AMP version of unpublished or otherwise access controlled nodes.
Simple AMP (Accelerated Mobile Pages) - Moderately critical - Access bypass - SA-CONTRIB-2019-071
Security release to fix Ubercart - Moderately critical - Cross-site-scripting
Ubercart - Moderately critical - Cross site scripting - SA-CONTRIB-2019-070
Two minor compatibility fixes for PHP 7.1 and above are also included.
No other significant changes have been made since the 7.x-3.12 release.