Bad news for Mint users who downloaded ISO files few days ago (20th Feb)…
Some dude found the way to replace the official Mint 17.3 Cinnamon ISOs with the cracked ISOs (with backdoor inside)
More details can be found here: http://blog.linuxmint.com/?p=2994
Also, as Clem announced, the forum database was compromised and you should change your password on all sensitive websites as soon as possible (in case you used the same password on other sites)
More details: http://blog.linuxmint.com/?p=3001