An issue was discovered in Poppler 0.74.0. There is a heap-based buffer over-read in the function Splash::blitTransparent at splash/Splash.cc.
https://gitlab.freedesktop.org/poppler/poppler/issues/750
https://lists.debian.org/debian-lts-announce/2019/06/msg00002.html
https://lists.debian.org/debian-lts-announce/2020/07/msg00018.html