The login form in Roundcube Webmail before 0.5.1 does not properly handle a correctly authenticated but unintended login attempt, which makes it easier for remote authenticated users to obtain sensitive information by arranging for a victim to login to the attacker's account and then compose an e-mail message, related to a "login CSRF" issue.

Roundcube 0.3.1 and earlier does not request that the web browser avoid DNS prefetching of domain names contained in e-mail messages, which makes it easier for remote attackers to determine the network location of the webmail user by logging DNS requests.