An on-line version of this announcement is available at http://www.postfix.org/announcements/postfix-2.6.2.html
Postfix stable release 2.6.2 fixes one defect in SASL support. This does not affect Postfix versions 2.5 and earlier.
With plaintext SMTP sessions AND smtpd_tls_auth_only=yes AND smtp_sasl_auth_enable=yes, the SMTP server logged warnings for reject_sender_login_mismatch, reject_authenticated_sender_login_mismatch, and reject_unauthenticated_sender_login_mismatch, instead of enforcing those restrictions.
You can find Postfix version 2.6.2 at the mirrors listed at http://www.postfix.org/
The same code is also available in Postfix snapshot 2.7-20090528. Postfix versions 2.5 and earlier are not affected.