I like my Crocs, but for me they are not a very good shoe for my feet.
I have one pair of Crocs that I bought last year. First thing I noticed was the textured footbed. It’s kinda spiky and not very comfortable to me. I have been amazed at all of the comfort claims due to this. You can and do get used to it, but the first couple of weeks is not comfortable at all.
Also, I’m a big guy and Crocs don’t offer much in the way of arch support. I have never had arch issues until I wore Crocs on a regular basis.
Do you have any Amazon add-ons (extensions) installed in Firefox? Did you, or someone who uses your computer, install any software recently?
If it is a Firefox add-on causing the issue and you have more than one that could be the culprit, start by disabling all of them. If that fixes the issue, then it is just a matter of enabling each add-on (one at a time) to discover which one is causing the issue. When you figure out which one it is, uninstall it.