It’s a glossy surface lit by an IES light (admittedly potentially overexposed?), but I can’t seem to figure out how to get rid of it. I followed Blender Guru’s 7 steps, which seem a bit outdated, and Denoiser won’t do anything for some reason.
This doesn’t seem to happen on blender 3.6.
Hello!
Could you maybe share a screenshot of your render settings?
Show us the difference between 3.6 and 4.0 with no denoising, I assume this is cycles?
IES seems to have more noise, but I don’t think it’s this much noise.
Isn’t it the surface roughness or bumper of the material. 
That’s what I was wondering, it may not be actual fireflies at all but the surface roughness at that glancing angle from the light.
Ok so sorry about the silence there - I was away from the computer for some time. And for some reason, it’s fixed once I stepped away and came back.
Edit: Actually incorrect - it seems that it’s to do with the amount of coat on the material. Since the wood portion is supposed to have a coat of resin on top, it’s meant to be reflective. The render turns out fine without the coat but with it it produces this result.