Pop-up authentication on closed thread

[chicfarmer1]

Today, I tried to access the thread
REALLY ONCE IN A LIFE TIME...only 3 in the country!!!!

and if I click the thread title or the most recent page of posts--but not the first page of posts--I get a pop-up authentication box that reads:
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Authentication Required
A username and password are being requested by http://www.huntinglodge.no
The site says "Temporarily Closed Pending Security Update"
with two boxes for username and password.
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Naturally, I clicked Cancel. I do not have cookies on my browser for this website, and it doesn't happen elsewhere at TRF.

Malware?