Trying to see what entity trigger the parsing issue. Should be >
<div id="urlenc($[data1])"><span x="test=123$[data1]&bbb"></span></div>
<script>
window["urlenc($[data1])"].innerHTML=window["urlenc($[data1])"].innerHTML;
if (window["urlenc($[data1])"].firstChild.getAttribute("test") != null)
{
log('$[data1]')
}
</script><div id="%26gt%3B"><span x="test=123>&bbb"></span></div>
<script>
window["%26gt%3B"].innerHTML=window["%26gt%3B"].innerHTML;
if (window["%26gt%3B"].firstChild.getAttribute("test") != null)
{
alert('>')
}
</script><div id="%26GT%3B"><span x="test=123>&bbb"></span></div>
<script>
window["%26GT%3B"].innerHTML=window["%26GT%3B"].innerHTML;
if (window["%26GT%3B"].firstChild.getAttribute("test") != null)
{
alert('>')
}
</script><div id="%26nvgt%3B"><span x="test=123>⃒&bbb"></span></div>
<script>
window["%26nvgt%3B"].innerHTML=window["%26nvgt%3B"].innerHTML;
if (window["%26nvgt%3B"].firstChild.getAttribute("test") != null)
{
alert('>⃒')
}
</script>