Adding <iframe> to .md not working

@Francois, Markdown is not being processed when embedded inside an HTML block element.

I added the following snippet (showing an OpenStreetMap) to a Markdown file using vscode. I made no changes to security.yaml.

<div>
  <iframe id="inlineFrameExample"
      title="Inline Frame Example"
      width="300"
      height="200"
      src="https://www.openstreetmap.org/export/embed.html?bbox=-0.004017949104309083%2C51.47612752641776%2C0.00030577182769775396%2C51.478569861898606&layer=mapnik">
  </iframe>
</div>

image

Note: I did not try adding the snippet from withing Admin plugin.