Craft CMS before 3.3.0 is susceptible to server-side template injection via the SEOmatic component that could lead to remote code execution via malformed data submitted to the metacontainers controller.
View the template here CVE-2020-9757.yaml
References:
https://github.com/nystudio107/craft-seomatic/commit/a1c2cad7e126132d2442ec8ec8e9ab43df02cc0f