This vulnerable really only works for servers that have cpanel running or installed.
Top shared hosting sites that resell cpanel.
Godaddy,Namecheap,OVHNET
The leakage occurs when the Mailman Archives lead back to the origin server.
Directory : /mailman/listinfo/mailman
Exploiter : https://github.com/Proxysec/cloudssp
I found this about 2 years ago just always privated it.
This works for sites that use cloudflare.
Credits to Nano