PHP remote file inclusion vulnerability in webmail.php in SquirrelMail before 1.4.4 allows remote attackers to execute arbitrary PHP code by modifying a URL parameter to reference a URL on a remote web server that contains the code.
The parseAddress code in (1) SquirrelMail 1.4.0 and (2) GPG Plugin 1.1 allows remote attackers to execute commands via shell metacharacters in the "To:" field.