PuTTY 0.81 security release

Version
0.81 of the PuTTY SSH client is out with a fix for CVE-2024-31497;
some users will want to update and generate new keys:

PuTTY 0.81, released today, fixes a critical vulnerability
CVE-2024-31497 in the use of 521-bit ECDSA keys
(ecdsa-sha2-nistp521). If you have used a 521-bit ECDSA private
key with any previous version of PuTTY, consider the private key
compromised: remove the public key from authorized_keys files, and
generate a new key pair.

However, this only affects that one algorithm and key size. No
other size of ECDSA key is affected, and no other key type is
affected.