Need to check for spam expolit vulnerability

The exploit relies on putting a newline, followed by a To:, Cc: or Bcc:

They do a Cc: to a certain address, which gathers info on where the exploits are, possibly for mass spam mailings later.

The solution for feedback was to issue a cryptic error (invalid data in field X) for possible exploits in any field.

It is a bit overzealous in that it does not check for a newline, but this is a sure way to prevent it, no matter what tricks they do.

Perhaps this should go into killes' mail.inc, and can be used to validate any data that is to be emailed. This way anyone using the common mail backend will get that validation for free?

The function that checks for that is like this:

function feedback_check_exploit($data) {
  $bad_strings = array (
    'To:',
    'Cc:',
    'Bcc:',
    'Content-Type:',
    'MIME-Version:',
    'Content-Transfer-Encoding:');

  foreach($bad_strings as $str) {
    if (stristr($data, $str)) {
      return true;
    }
  }
  return false;
}