If you downloaded Mint Cinnamon today (for versions of "today" that include February 20th, 2016) you should immediately check the MD5 checksum. Blog Entry here.
From Clem:
We were exposed to an intrusion today. It was brief and it shouldn't impact many people, but if it impacts you, it's very important you read the information below.
Hackers made a modified Linux Mint ISO, with a backdoor in it, and managed to hack our website to point to it.
As far as we know, the only compromised edition was Linux Mint 17.3 Cinnamon edition.
If you downloaded another release or another edition, this does not affect you. If you downloaded via torrents or via a direct HTTP link, this doesn't affect you either.
Finally, the situation happened today, so it should only impact people who downloaded this edition on February 20th.
Apparently the hacked ISOs are hosted on 5.104.175.212 and the backdoor connects to absentvodka.com. Both lead to Sofia, Bulgaria, and the name of 3 people over there.
The comment thread suggests that the ISOs are showing up in other places, and that the Mint site may still not be entirely secure.
(Score: 2) by Fnord666 on Thursday February 25 2016, @04:25PM
A good point. A phone call to the entity in question (not using a phone number you got from the same web page as the download!!) would be one way. A PGP signed email reply from the entity in question, where the public key has been published for a number of years on a public key database is another. My own efforts trying to get a valid fingerprint from someone has met with limited success as well.