A critical vulnerability was found in glibc recently.
glibc is a Linux foundamental C library, which is being shared by a number of Linux program.
If you are managing a server (or VPS, or cloud server, or else) with Linux (e.g. CentOS 6, CentOS 7, Debian, …), you shall consider to immediately update your operating system (and preferably reboot) to prevent website hacking or server hacking.
In case of remote arbitrary code execution, it can easily be uploaded back door, and deface (infect) all websites in the same server.