-Security fix: if an SSH server accepted an offer of a public key and then rejected the signature, PuTTY could access freed memory, if the key had come from an SSH agent.
-Security feature: new config option to disable PuTTY's dynamic host key preference policy, if you prefer to avoid giving away to eavesdroppers which hosts you have stored keys for.
-Bug fix: the installer UI was illegible in Windows high-contrast mode.
-Bug fix: console password input failed on Windows 7.
-Bug fixes in the terminal: one instance of the dreaded "line==NULL" error box, and two other assertion failures.
-Bug fix: potential memory-consuming loop in bug-compatible padding of an RSA signature from an agent.
-Bug fix: PSFTP's buffer handling worked badly with some servers (particularly proftpd's mod_sftp).
-Bug fix: cursor could be wrongly positioned when restoring from the alternate terminal screen. (A bug of this type was fixed in 0.59; this is a case that that fix missed.)
-Bug fix: character cell height could be a pixel too small when running GTK PuTTY on Ubuntu 20.04 (or any other system with a similarly up-to-date version of Pango).
-Bug fix: old-style (low resolution) scroll wheel events did not work in GTK 3 PuTTY. This could stop the scroll wheel working at all in VNC.
- Security fix: on Windows, a server could DoS the whole Windows GUI by telling the PuTTY window to change its title repeatedly at high speed.
- Pageant now supports loading a key still encrypted, and decrypting it later by prompting for the passphrase on first use.
- Upgraded default SSH key fingerprint format to OpenSSH-style SHA-256.
- Upgraded private key file format to PPK3, with improved passphrase hashing and no use of SHA-1.
- Terminal now supports ESC [ 9 m for strikethrough text.
- New protocols: bare ssh-connection layer for use over already-secure IPC channels, and SUPDUP for talking to very old systems such as PDP-10s.
- PuTTYgen now supports alternative provable-prime generation algorithm for RSA and DSA.
- The Unix tools can now connect directly to a Unix-domain socket.