Recently in the update 4.7.4 wordpress added an option to the target="_blank" because a vulnerability in their editor tinymc adding rel="noopener noreferrer" by default when _blank was selected

https://github.com/tinymce/tinymce/issues/3177

https://www.tinymce.com/docs/changelog/#version450-november232016

https://dev.to/ben/the-targetblank-vulnerability-by-example

anyone can hack your system with the window.opener vulnerability

as far we use ux-builder and not tinymce was good to change by default