Serious PHP Issues Revealed by Flaws in PHPMailer, SwiftMailer
Experts have determined that the remote code execution vulnerabilities affecting the PHPMailer and SwiftMailer email-sending libraries are caused by PHP design flaws.
Read more: Serious PHP Issues Revealed by Flaws in PHPMailer, SwiftMailer
Story added 30. December 2016, content source with full text you can find at link above.