At the time of writing the the homepage of mailing list domain was showing the two list-
The GreaT TeAm was the same hackers group who have also hacked Egyptian Ministry of Information Website two days before, and they also defaced a NATO subdomain .
After Contacting to the hackers team, they reported that, "kali team didnt check the security for mailmanlist.net before the linked thier domain "mailmanlist". The mailing list domain of Kali Linux is hosted on the Mailmanlist, and Mailmanlist website is Vulnerable to Heartbleed vulnerability.
After exploiting the Heartbleed vulnerability, hackers have managed to gain access to the mailmanlist users account vai stolen cookies and then searched for more vulnerable web applications. This allows him to gain the administrative credentials of Kali Linux Mailing list account.