There is 1 open security issue in bullseye.
1 issue left for the package maintainer to handle:
opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters. For example, it allows command execution via a crafted GECOS field whereas systemd-sysusers (a program with the same specification) does not do that.
You can find information about how to handle this issue in the security team's documentation.