Details see:
https://github.com/ckeditor/ckeditor4/security/advisories/GHSA-m94c-37g6-cjhc ( CVE-2021-37695 )
https://github.com/ckeditor/ckeditor4/security/advisories/GHSA-6226-h7ff-ch6c ( CVE-2021-32808 )
https://github.com/ckeditor/ckeditor4/security/advisories/GHSA-7889-rm5j-hpgg ( CVE-2021-32809 )