SUSE's Security Team has published a detailed blog post on their recent review of the Plasma Login Manager version 6.6.2, which was forked from the SDDM display manager.

While most of the code remains the same, the new upstream added a privileged D-Bus helper called plasmaloginauthhelper, which suffers from defense-in-depth security issues.

[...] Based on the high severity of the defense-in-depth issues shown in this report, our assessment is that there is effectively no separation between root and the plasmalogin service user account.

At this time there is no bugfix available by upstream, but a security fix is planned for the next Plasma release on May 12. We have not been involved in upstream's bugfix process so far and have no knowledge about the approach that will be taken to address the issues from this report.

Security updates have been issued by AlmaLinux (firefox, gdk-pixbuf2, java-17-openjdk, libxml2, python3, python3.11, python3.12, sudo, and webkit2gtk3), Debian (dnsdist, node-tar, pdns, pdns-recursor, and policykit-1), Fedora (chromium, edk2, and vim), Oracle (firefox, gdk-pixbuf2, go-toolset:rhel8, libpng12, LibRaw, libxml2, python, python3, python3.11, python3.12, python3.12-wheel, vim, webkit2gtk3, xorg-x11-server, xorg-x11-server-Xwayland, yggdrasil, and yggdrasil-worker-package-manager), Red Hat (container-tools:rhel8, delve, git-lfs, go-rpm-macros, grafana, grafana-pcp, osbuild-composer, and rhc), SUSE (bouncycastle, clamav, container-suseconnect, dovecot22, erlang, firefox, fontforge, freerdp2, ghostscript, giflib, gnome-remote-desktop, go1.25, go1.26, google-guest-agent, haproxy, ignition, ImageMagick, kernel, libcap, libpng16, libraw, librsvg, mariadb, openexr, pocketbase, protobuf, python-Pillow, python-requests, qemu, rust1.94, sudo, tomcat, tomcat10, tomcat11, webkit2gtk3, and xen), and Ubuntu (dotnet10, dovecot, linux-nvidia-lowlatency, node-follow-redirects, openssh, packagekit, python-cryptography, python-tornado, ruby-rack-session, ujson, and wheel).