Both angle braces must be escaped

[antelle]

https://www.w3.org/TR/2014/CR-DOM-Parsing-20140617/#serializing

1. If the require well-formed flag is set (its value is true), and node's data contains characters that are not matched by the XML Char production [XML10], then throw an exception; the serialization of this node's data would not be well-formed.
2. Let markup be the value of node's data.
3. Replace any occurrences of "&" in markup by "&".
4. Replace any occurrences of "<" in markup by "&lt;".
5. Replace any occurrences of ">" in markup by "&gt;".
6. Return the value of markup.

Please add > to the list of escaped characters here (and above as well).
But this will break this test. Why are you expecting > to be left as is? This is not standard behavior.
Try this in browser:

var doc = new DOMParser().parseFromString('<test/>', 'text/xml');
doc.documentElement.appendChild(doc.createTextNode('hello ]]> there'));
new XMLSerializer().serializeToString(doc) // "<test>hello ]]&gt; there</test>"

Such behavior was added in 47fa9b8

[saschanaz]

This issue breaks prettify-xml which depends on angle braces for indentation.

<constructor>
  <param name="paths" type="sequence&lt;Path2D>"/>
    <param name="fillRule" optional="1" type="CanvasFillRule"/><!-- broken -->
  </constructor>

[Holzhaus]

PR #207 should fix this without breaking prettify-xml.

[saschanaz]

It seems there already is a relevant PR. #132

(Though it should also be added on attributes)

[karfau]

Conversation can be continued in xmldom/xmldom#58 since this is currently the place where the project is being maintained.