A Server Side Template Injection (SSTI) was discovered in the SEOmatic plugin before 3.1.4 for Craft CMS, because requests that don’t match any elements incorrectly generate the canonicalUrl, and can lead to execution of Twig code.
ha.cker.info/exploitation-of-server-side-template-injection-with-craft-cms-plguin-seomatic/
github.com/nystudio107/craft-seomatic/commit/1e7d1d084ac3a89e7ec70620f2749110508d1ce1
github.com/nystudio107/craft-seomatic/releases/tag/3.1.4
twitter.com/nystudio107/status/1021847835418009605
twitter.com/nystudio107/status/1021855169515057152
www.exploit-db.com/exploits/45108/