Occasional google ad download when opening a page

[Rod200SX]

Having a tempremental issue that of course I can't seem to replicate but occasionally when I click in to a thread, a window appears (not a pop up, an actually microsoft window) pops up as though I've clicked to download a text document with the name of something like "google Ad" as the file name.

It's nothing malicious, I think something jazzy going on with the adverts. I've just habitually closed it on the couple times it's done it but as above, I unfortunately can't seem to replicate it.

This is on PC, mozilla firefox with no ad blockers, it that helps at all.

ETA: Managed to grab a screenshot

Edited by Rod200SX on Wednesday 23 September 22:52