The third-party links with target="_blank" attribute and no rel="noopener noreferrer" attribute allows linked page partial access to the linking page window object. object of the original page to the linked page via window.opener object.This can be exploited for phishing attacks if the linked page is malicious.
So in your case If this is coming from RTE only then you need to place this as an authoring guildeline, But however , if this is coming from a hyperlink or CTA component then you should handle this programmatically, you can write an utility which identifies whether an link is external or not and based on that plance rel="noopener noreferrer" with the anchor tag.