Pretty sure I reported this a good while back, on an earlier version of IPS 4 - but it's back on 4.5
Steps to reproduce (tested on Firefox & Chrome)
Create a new topic or a reply
Paste an embeddable Youtube link (e.g. https://www.youtube.com/watch?v=URJH3ZJzxB0)
After it embeds, look below the attachment section of the editor
Result:
Create New Topic - Invision Community - Mozilla Firefox 2020-10-11 15-50-12.mp4