Log Message:
putty: update to 0.81.

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.