Chrome. I personally have never seen it but some users have which I can't ask directly.
They are using Chrome but I'm not confident it is an up to date version.
The bug reports on the web about this error message go back to
2019 and were more frequent around that time than now.
What I'd like to see from Google is
"We fixed that bug in version XX".
I've searched for such a statement and couldn't find it both on the web
and in Google's own help pages.
Entering the exact error message into Google yields nothing of value.