What is causing the red "invalid-markup" box to appear next to these equations?

[mdonovan1]

We are having an issue with red "invalid-markup" boxes showing next to equations created using the built-in Canvas math equation tool.  These boxes only appear when using Firefox.  They do not appear in Chrome.  I have included screenshots of the issue, along with a screenshot of the HTML for this page.  I'm not sure what might be causing the issue.  Does it relate to something about how Firefox picks up the HTML for the math equations?

[kona · Accepted solution]

 @mdonovan1 , greetings! This is an interesting/strange issue. My recommendation is to contact Canvas Support to see if they are aware of the issue and to see if they can help. To do this, click on the Help link in Canvas and "Report a Problem." Please let us know what support has to say!

Kona

[James]

 @mdonovan1  

It looks like the problem is with MathML that is not part of the equation. That would make sense why it shows up in Firefox but not Chrome (Chrome doesn't support MathML). According to the Mozilla Developer Network, the MathML mi element is really only supported by Firefox.

Try going into the editor's HTML view and finding the portion right after the paragraph element and before the image. The hidden-readable class isn't in my HTML editor view and when I view it in the browser, it comes after the equation image. That suggests that there's something in there that shouldn't be. Perhaps you copy/pasted from somewhere and it brought some crud along with it.

[breklis]

We are also seeing a red box around a student response when the student uses the equation editor in an "essay question" answer.  It makes it appear that the answer is incorrect.  Could this be related?  It's happening in Chrome.

Here is what it looks like: