A critical security issue in the Xen virtualization software will become public on Tuesday, November 22nd 2016. The Xen team has already informed Gandi of the necessary patches.
Following this announcement, we have pre-emptively deployed the patches required to correct the issue. We have been monitoring the particular security flaw, and have determined that we will need to stop/start certain Xen VMs in order to assure that no further attack vector remains.
Warning: a simple "reboot" of the concerned servers is not enough. They must be stopped and started in order to apply the security measures.
As always, if you have any questions or need of assistance, please do not hesitate to contact our Customer care team.