Math input error when mixing MathML and a HTML hyperlink

[samimaattaCelia]

Issue Summary

MathJax 4 produces a math input error when rendering a MathML equation that also has other HTML elements in it.

OS: Windows 11
Browser: Mozilla Firefox 153.0

Expected output (using Firefox's native rendering):

Steps to Reproduce:

Render the MathML equation in question:

<math xmlns="http://www.w3.org/1998/Math/MathML">
        <mo>|</mo>
        <mi>x</mi>
        <mo>+</mo>
        <mi>y</mi>
        <mo>|</mo>
        <mo>&lt;</mo>
        <mo>|</mo>
        <mi>x</mi>
        <mo>|</mo>
        <mo>+</mo>
        <mo>|</mo>
        <mi>y</mi>
        <mo>|</mo>
        <mtext>
        <sup>
            <a href="https://en.wikipedia.org/wiki/Triangle_inequality">Triangle inequality (Wikipedia)</a>
        </sup>
        </mtext>
      </math>

It is a bug, since it should be possible to have HTML markup inside MathML markup as per MathML Core 2.2.1 HTML and SVG.

Technical details:

• MathJax Version: 4
• OS: Windows 11
• Browser: Mozilla Firefox 153.0

I am using the following the default MathJax configuration.

Loading MathJax via:

<script src="https://cdn.jsdelivr.net/npm/mathjax@4/tex-mml-chtml.js" defer></script>

[dpvc]

Because embedding HTML inside MathML is a potential security issue for sites that allow readers to enter mathematics (like question & answer sites), MathJax's support for HTML in MathML requires the page author to opt-in by setting the allowHtmlInTokenNodes configuration option in the mml section of the Mathjax configuration to true. So use

<script>
MathJax = {
  mml: {
    allowHtmlInTokenNodes: true
  }
};
</script>

jest before the script that loads tex-mml-chtml.js.

[samimaattaCelia]

Okay, great! Thanks for the answer.