Millions of sites WordPress were attacked this week, said Defiant, the company behind the Wordfence firewall.
It is not known how they discovered it 0day, but all last week the hackers started looking for sites that had the add-on installed.
If the detection was successful, the attackers took advantage of it 0day and uploaded a web shell disguised as an image file to the victim's server. So they could access the site by adding it to a botnet.
The attacks started late, but intensified throughout the past week. Defiant has detected attacks against 1 million websites with WordPress, just on Friday, September 4th.
In all, Defiant has blocked attacks on more than 1,7 million websites since September 1, when the attacks were first discovered.
The good news is that his team of developers File Manager created and released an update for 0day the same day he learned of the attacks. Some administrators installed the update immediately, but as usual, there are others who did not.