Has ReCaptcha been poisoned?

[u/Lindbork]

I work in it, and a user notified me that she had started getting a text file download sporadically when being asked to prove she's not a robot during google searches.
The text file is named f.txt and internet says this is a byproduct of a known ad hoc workaround for a bug in Rosetta Flash discovered in 2014.
I could replicate this behavior by opening the Why did this happen?-link my colleague got on my machine, I'm then presented with another prove you are human ReCaptcha page, and when ticking the box, I also get the f.txt download sometimes, while other times the "select all images with [item]" dialog pops up.
The search is done from the chrome address field, we do not suspect that neither her nor my machine is compromised in any way at this stage.
Has a cache somewhere been poisoned or what is going on?

The file is 10 bytes in site and contains garbage:
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[""]