A zsh security update has been released for Debian GNU/Linux 10 and 11 to address an issue where an attacker can execute arbitrary commands into a user's shell.

DSA 5078-1: zsh security update

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Debian Security Advisory DSA-5078-1 security@debian.org
  https://www.debian.org/security/ Sebastien Delafond
February 16, 2022   https://www.debian.org/security/faq
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Package : zsh
CVE ID : CVE-2021-45444

It was discovered that zsh, a powerful shell and scripting language,
did not prevent recursive prompt expansion. This would allow an
attacker to execute arbitrary commands into a user's shell, for
instance by tricking a vcs_info user into checking out a git branch
with a specially crafted name.

For the oldstable distribution (buster), this problem has been fixed
in version 5.7.1-1+deb10u1.

For the stable distribution (bullseye), this problem has been fixed in
version 5.8-6+deb11u1.

We recommend that you upgrade your zsh packages.

For the detailed security status of zsh please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/zsh

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/