Basically it's possible to inject dirty html:

const striked = '<strike>test</strike>';

console.log(<div>{striked}</div>);
console.log(<div><strike>test</strike></div>);
console.log(<div>{striked}</div>);

This is the output:

<div>&lt;strike&gt;test&lt;/strike&gt;</div>
<div><strike>test</strike></div>
<div><strike>test</strike></div>

Expected output:

<div>&lt;strike&gt;test&lt;/strike&gt;</div>
<div><strike>test</strike></div>
<div>&lt;strike&gt;test&lt;/strike&gt;</div>

After rendering <div><strike>test</strike></div>, it caches <strike>test</strike> and doesn't sanitize it anymore. It can be seen live here as well. Just because something was rendered before, it shouldn't mean that it's sanitized.