A composer security update has been released for Debian GNU/Linux 10 to address an arbitrary code execution issue.

DSA 4907-1: composer security update

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Debian Security Advisory DSA-4907-1 security@debian.org
  https://www.debian.org/security/ Sebastien Delafond
April 29, 2021   https://www.debian.org/security/faq
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Package : composer
CVE ID : CVE-2021-29472

It was discovered that composer, a dependency manager for PHP, did not
properly sanitize Mercurial URLs, which could lead to arbitrary code
execution.

For the stable distribution (buster), this problem has been fixed in
version 1.8.4-1+deb10u1.

We recommend that you upgrade your composer packages.

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

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/