Why does my CPU usage spike by about 45% on UK PCGamer?

[XP2k20]

Drops down again on the forums but the regular site my CPU spikes substantially. Why? Is it just a badly optimised webpage or is it something shady like mining crypto?

 

[Sarafan]

Drops down again on the forums but the regular site my CPU spikes substantially. Why? Is it just a badly optimised webpage or is it something shady like mining crypto?

This is an issue experienced by Firefox users for some reason. Check this thread: https://forums.pcgamer.com/threads/ff-website-uses-lots-of-cpu.4099/. No fix at this moment.