KDE Okular before 1.10.0 allows code execution via an action link in a PDF document.
https://security.gentoo.org/glsa/202007-47
https://lists.debian.org/debian-lts-announce/2021/12/msg00019.html
https://lists.debian.org/debian-lts-announce/2020/03/msg00033.html
https://kde.org/info/security/advisory-20200312-1.txt
https://invent.kde.org/kde/okular/-/commit/6a93a033b4f9248b3cd4d04689b8391df754e244