PuTTY 0.62 fixes a security issue present in 0.59, 0.60 and 0.61.
If you log in using SSH-2 keyboard-interactive authentication
(which is the usual method used by modern servers to request a
password), the password you type was accidentally kept in PuTTY's
memory for the rest of its run, where it could be retrieved by
other processes reading PuTTY's memory, or written out to swap
files or crash dumps.