https://files.catbox.moe/g1bejn.png

When I visit the site from Safari on macOS I see this in the console. Are there any particular services that use port 8888 for the website to do this?

https://my.f5.com/manage/s/article/K000138794

It seems to be part of some "bot defense" product by these F5 people, to "test the different browser capabilities". I doubt it's intended to hit a real endpoint on any system.