Answer by djibe for With Hugo, can we use HTML code in a md file?

From version 0.6, Hugo uses Goldmark for markdown.

For security reasons, Goldmark wipes HTML code.

However, if you use HTML frequently in your site, you can add to your config.toml

[markup.goldmark.renderer]  unsafe = true # Allow HTML in md files

For a less frequent usage of HTML, you can add safeHTML parameter to your HTML string (Hugo doc for safeHTML).