Security Vulnerability in APOP Authentication — Mozilla

Gaëtan Leurent informed us of a weakness in APOP authentication that could allow an attacker to recover the first part of your mail password if the attacker could interpose a malicious mail server on your network masquerading as your legitimate mail server. With normal settings it could take several hours for the attacker to gather enough data to recover just a few characters of the password. This result was presented at the Fast Software Encryption 2007 conference.