The remote Debian host is missing a security-related update.
Dawid Golunski discovered that PHPMailer, a popular library to send email from PHP applications, allowed a remote attacker to execute code if they were able to provide a crafted Sender address. Note that for this issue also CVE-2016-10045 was assigned, which is a regression in the original patch proposed for CVE-2016-10033. Because the origial patch was not applied in Debian, Debian was not vulnerable to CVE-2016-10045.
Upgrade the libphp-phpmailer packages. For the stable distribution (jessie), this problem has been fixed in version 5.2.9+dfsg-2+deb8u2.