I've noticed this with many WordPress projects (and clients) over the years so I thought it was worth a public thread. When you interlink a post/page that has embedding enabled, the iframe source will affix /embed/ URL suffix: <iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="position: absolute; clip: rect(1px, 1px, 1px, 1px);" title="Example"...
Originally asked by Jesse Nickles on Stack Exchange (wordpress) (CC BY-SA 4.0).