Wordfence’s Threat Intelligence team discovered a vulnerability present in two themes by Elegant Themes, Divi and Extra, as well as Divi Builder, a WordPress plugin. Combined, these products are installed on an estimated 700,000 sites. This flaw gave authenticated attackers, with contributor-level or above capabilities, the ability to upload arbitrary files, including PHP files, and achieve remote code execution on a vulnerable site’s server.

This flaw made it possible for authenticated users with the edit_posts capability, like contributors, editors, and authors, to upload arbitrary files. An attacker could easily upload malicious PHP files and access them from the uploads directory. This could ultimately result in remote code execution and complete compromise of a vulnerable site’s hosting account.

Fortunately, Elegant Themes was very quick to respond and release a patch that not only prevented all files except .json files from being uploaded, but also ensured that files would be sufficiently deleted at any stage of the process once no longer used.

As long as you have supplied your Elegant Themes Username and API key on your WordPress site, then you can take care of your updates directly in the updates area on your site. To do so, log into your site, and navigate to the “Updates” area. Select the Elegant Themes product you would like to update and just click “Update Plugin” or “Update Theme” depending on which product you are updating.

Also, please note that Elegant Themes has made this patch available to users, even if your account is expired.

If you are unable to update fully, you can install Elegant Themes Security Patcher Plugin that will temporarily patch the vulnerability until you are able to do a complete update.

Source: https://www.wordfence.com/blog/2020/08/critical-vulnerability-exposes-over-700000-sites-using-divi-extra-and-divi-builder/

Unfortunately, you have to have a paid account to be able to access the Elegant Themes Security Patcher Plugin, it seems that this file should not be behind a paywall.