I am using the web app on Firefox 103 on Ubuntu 22.04.
I was editing a note and left the web page open while I was checking something in my notebook when I noticed that my CPU fan had kicked on high. I opened the Firefox Task Manager and noticed the Evernote tab was sitting stably at 110% usage of a core. In the developer tools I took a performance snapshot and it looks like the runtime garbage collector was running for long periods despite the page just sitting with no interaction from the user.
I couldn't debug any more than this, but this much CPU usage from a WYSIWYG editor on a webpage seems pretty unacceptable. Happy to take a performance capture or something if you don't have this particular environment available or can't recreate it.