Adding a hero icon to heading 2 and 3 causes on-page menu (right menu) to show jibberish

[thedevilfish]

Description

Adding hero icons using instructions provided in: https://imfing.github.io/hextra/docs/guide/shortcodes/icon/ causes righthand sidebar to display HAHAHUGOSHORTCODE11s1HBHB

Steps To Reproduce

1. Started hugo on localhost with the following parameters: hugo server --buildDrafts --disableFastRender

2. Create a page with the following markdown

# {{<icon "ticket">}} Ticket Icon in title

This is a ticket section

## {{<icon "exclamation">}} Exclamation Icon in title

This is an exclamation section

### {{<icon "arrow-right">}} Arrow Right Icon in title

This is an arrow right section

## {{<icon "arrow-left">}} Arrow Left Icon in title

This is an arrow left section

3. Point to localhost:1313 and see the results

Expected Behavior

Icons should render or be excluded from the navigation rendering

Actual Behavior

righthand sidebar to display HAHAHUGOSHORTCODE11s1HBHB

Screenshots

See result:

Environment

• Hugo Version: hugo v0.150.0+extended+withdeploy darwin/arm64 BuildDate=2025-09-08T13:01:12Z VendorInfo=brew
• Browser/OS: Chrome / MacOS
• Theme Version: 0.11.1

Additional Context

N/A

[imfing]

The icon shortcode is not recommended to be used in a Markdown heading