It may be due to the fact that the *Tor* Browser access the 'Deep Web' which has many malicious applications available.
Could you provide what the quarantined item is?
Grab the file and submit it to www.virustotal.com and see what the detection rate is. that would give you an idea while CD helps you
Thank you for your replies. I haven't done anything particular, but when I tried to download the file again today, it went through without any problems. So the case solved itself.
Strange things happen or someone else requested a review.