Web security firm Sucuri has reported on the discovery of a WordPress plugin vulnerability affecting any site that uses the genericons package.
At this time, the JetPack plugin (installed on over 1 million sites) and the TwentyFifteen theme (installed by default) have been identified as vulnerable. Apparently, any plugin is potentially vulnerable if it includes the example.html file that comes with the genericons package.
That being said, the simple fix to protect yourself from this vulnerability is to remove the example.html file from the genericons package, which is unnecessary to begin with.
Sucuri managed to detect this vulnerability before it was disclosed, which means it has had literally zero days in the wild. Due to the quick response time, this vulnerability is said to have low severity, but Sucuri warns that it’s easy to exploit.
If you’re interested in the more technical details of this vulnerability, it’s described to work as follows:
“DOM-Based XSS is an XSS attack wherein the attack payload is executed as a result of modifying the Document Object Model (DOM) “environment” in the victim’s browser used by the original client side script, so that the client side code runs in an “unexpected” manner. That is, the page itself (the HTTP response that is) does not change, but the client side code contained in the page executes differently due to the malicious modifications that have occurred in the DOM environment.”
Sucuri had the foresight to reach out to web hosts to have them virtually patch the vulnerability. The following hosts are confirmed to have rolled out the virtual patch:
If your website is hosted with one of the above companies, you’re protected. If your site is hosted with a different company it’s up to you to manually fix the issue. Sucuri highly recommends removing the example.html from inside the genericons directory.