No, sorry, I don't work for Instructure. Just a software developer and support at a customer institution. Trying to get ahead of this issue if it starts coming up for us to be able to provide as much feedback as possible to Canvas support and also personally curious about the cause of this.
I was trying to reproduce this so I could profile the page like @ChristopherRobe had but it hasn't caused a problem for me. I also haven't seen this reported locally this week, but have heard of other schools where this is happening.
Based on that users Firefox page Profile it looks like it something related to an LTI tool with the Window.postMessage being called so frequently, but not sure where.
Thanks for the information! Hope this gets resolved soon.