SquirrelMail is a standards-based webmail package written in PHP4.
A bug was found in the way SquirrelMail handled the $_POST variable. If a user is tricked into visiting a malicious URL, the user's SquirrelMail preferences could be read or modified. The Common Vulnerabilities and Exposures project assigned the name CAN-2005-2095 to this issue.
All users of SquirrelMail should upgrade to this updated package, which contains backported patches that resolve these issues.