Steps to reproduce
Post > New Work
Fill in required information
In the work content, paste the embed code for a YouTube video, e.g. <iframe width="560" height="315" src="https://www.youtube.com/embed/yPQfcG-eimk" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
If you click play on the video, it says the video is unavailable.
What should happen
The video should play.
How to test
Check that YouTube embeds can play, especially ones that are currently broken on beta.
Test again (e.g. for Twitter requests) again but expect the header Referer: https://archiveofourown.org/ where it used to be none.