htmlpurifier - How to escape self closing tags?

Question

I have noticed that when passing html string to htmlpurifier, it replaces all self closing tags either by open and closing tags or by just open tags

example

Before purifying

<p>
  <math xmlns="http://www.w3.org/1998/Math/MathML">
    <mmultiscripts>
       <mi>y</mi>
       <mprescripts/>
       <none/>
       <mn>2</mn>
    </mmultiscripts>
   </math>
</p>

After purifying

<p>
   <math xmlns="http://www.w3.org/1998/Math/MathML">
     <mmultiscripts>
       <mi>y</mi>
       <mprescripts></mprescripts>
       <none>
         <mn>2</mn>
      </mmultiscripts>
    </math>
 </p>

As you see the <none/> tag was replace after purifying by <none> tag Which destroyed the render of the html !

What to add in my configurations file in order to escape self closing tag? Is there any shorthand from this list can solve the problem ?

Please note that I am using htmlpurifier through mews/purifier package which is a package specific for laravel integration.

Answer 1

I believe the Empty rule for the <none> tag may point to why the closing tag disappears. HTML Empty tags, like <br>, <hr> and <img>, self-close implicitly. But you may be able to use an Inline element with a Custom rule for allowed children that's an empty regex.

Is the 'open and closing tags' scenario a problem for you? I'm not familiar enough with MathML to know whether this isn't just a cosmetic change; if the semantic behaviour of that code remains the same, I wouldn't worry about it. I don't currently know how to solve that one.