A similar problems happens with <tags> inside backticks. It also makes the parsedown.org/extra website crash with a 500 response code:

<section markdown="1">
An example `<style>` tag.
</section>

Passing this section through the parse method breaks later content (a tags are not closed properly, for example).

I have the same issue. On my local machine everything works fine. But on the production server the parsing breaks. The local machine and the production server have the same PHP Version.

• PHP 7.4.8
• Parsedown 1.8.0-beta-7
• ParsedownExtra 0.8.0

<div markdown="1">
<ul>
<li>Foo</li>
<li>Bar</li>
</ul>

<ul>
<li>Second Foo</li>
<li>Second Bar</li>
</ul>
</div>

On the production server the second list with Second Foo and Second Bar disappear. On the local machine the second list appears.

<div>
<ul>
<li markdown="1">Foo</li>
<li markdown="1">Bar</li>
</ul>

<ul>
<li markdown="1">Second Foo</li>
<li markdown="1">Second Bar</li>
</ul>
</div>

If only the inner tags have the markdown attributes the second list will be appeared on the production server.

I hope I've found the cause. PR is created #155

DOMDocument trim the new line characters in some PHP environments.