http://www.bbc.co.uk/news/technology-26969629

Dubbed "Heartbleed", the exploit takes advantage of a vulnerability in OpenSSL that allows hackers to read data and retrieve passwords.

Reports say that hackers could have been using this exploit for at least 2 years, before it was made public, so you should change passwords to decrease the chance of your account(s) being stolen since a large number of "hackers" will start using this.

Corporations like Facebook and Google have said that they had already patched the bug well before it became public, so no risk here, however Witendofi could be at big risk. Be very wary if people actually start using Witendofi for the next couple of hours because they may not be who they say they are and try and scam you for all your DS games.