On June 16, 2022, the Wordfence Threat Intelligence team noticed a back-ported security update in Ninja Forms, a WordPress plugin with over one million active installations. As with all security updates in WordPress plugins and themes, our team analyzed the plugin to determine the exploitability and severity of the vulnerability that had been patched.
We uncovered a code injection vulnerability that made it possible for unauthenticated attackers to call a limited number of methods in various Ninja Forms classes, including a method that unserialized user-supplied content, resulting in Object Injection. This could allow attackers to execute arbitrary code or delete arbitrary files on sites where a separate POP chain was present.
There is evidence to suggest that this vulnerability is being actively exploited in the wild, and as such we are alerting our users immediately to the presence of this vulnerability.
This flaw has been fully patched in versions 188.8.131.52, 3.1.10, 3.2.28, 184.108.40.206, 220.127.116.11, 18.104.22.168, and 3.6.11.WordPress appears to have performed a forced automatic update for this plugin, so your site may already be using one of the patched version. Nonetheless, we strongly recommend ensuring that your site has been updated to one of the patched versions as soon as possible since automatic updates are not always successful.