In a recent pentest I was able to execute a XSS in an Angular quill rich text editor .
<p><style>@keyframes x{}</style><strong style='animation-name:x' onanimationstart='alert(1)'></strong></p>
Lunch quill editor as a component in stackblitz.io platform and inject payload as shown in the image.
Any other payloads are blocked, but not this one.
In a private pentest, attack was done in server side not just client side. The content of the message was inserted using a POST request using the description field, leading to a stored XSS.
This solution might be found in other implementations of quill editor.
"We've decided that the issue you reported is not severe enough for us to track it as a security bug".