The kramdown gem before 2.3.0 for Ruby processes the template option inside Kramdown documents by default, which allows unintended read access (such as template="/etc/passwd") or unintended embedded Ruby code execution (such as a string that begins with template="string://<%= `). NOTE: kramdown is used in Jekyll, GitLab Pages, GitHub Pages, and Thredded Forum.
Reference and upstream commit:
Created rubygem-kramdown tracking bugs for this issue:
Affects: epel-7 [bug 1858415]
Affects: fedora-all [bug 1858414]
Upstream advisory: https://kramdown.gettalong.org/news.html
Rubygem-kramdown is not shipped in Red Hat Enterprise Linux 8 and is only used as a buildtime dependency only. Customers are not at risk for exploitation of this flaw.