From the “if you have to use <cough> Windows </cough>” file…
From the Putty home page:
Latest news
2004-08-03 SECURITY HOLE, fixed in PuTTY 0.55
PuTTY 0.55, released today, fixes a serious security hole which may allow a server to execute code of its choice on a PuTTY client connecting to it. In SSH2, the attack can be performed before host key verification, meaning that even if you trust the server you think you are connecting to, a different machine could be impersonating it and could launch the attack before you could tell the difference. We recommend everybody upgrade to 0.55 as soon as possible.