Source: Hackers Already Trying to Exploit Serious PHP Flaw.
“Estimated 70% of websites” including all WordPress sites which runs on PHP. Emergency patches should be already available, you may have to add a relevant repository prior to update.
Please visit PHP2shell.com for more details.
Entire websites are being preemptively taken down to avoid hacking, while IT departments implement updates. Many repositories are failing to respond under the load of most of the world’s servers updating all at once. And then we have news of Hackers already using the exploit makes for a super-happy-fun-time for server administrators.