Can a user drop a HTML Shadow DOM into a blog post?

It looks like this plugin may make it possible:

Code Embed – WordPress plugin | WordPress.org https://wordpress.org/plugins/simple-embed-code/

However I don’t use WordPress any more. Is there someone here that can confirm it will work?

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)