CVE-2021-29472

Composer is a dependency manager for PHP. URLs for Mercurial repositories
in the root composer.json and package source download URLs are not
sanitized correctly. Specifically crafted URL values allow code to be
executed in the HgDriver if hg/Mercurial is installed on the system. The
impact to Composer users directly is limited as the composer.json file is
typically under their own control and source download URLs can only be
supplied by third party Composer repositories they explicitly trust to
download and execute source code from, e.g. Composer plugins. The main
impact is to services passing user input to Composer, including
Packagist.org and Private Packagist. This allowed users to trigger remote
code execution. The vulnerability has been patched on Packagist.org and
Private Packagist within 12h of receiving the initial vulnerability report
and based on a review of logs, to the best of our knowledge, was not abused
by anyone. Other services/tools using VcsRepository/VcsDriver or
derivatives may also be vulnerable and should upgrade their
composer/composer dependency immediately. Versions 1.10.22 and 2.0.13
include patches for this issue.