In WordPress 5.0, which was released in December 2018, a new editor was introduced, known as the block editor or Gutenberg. In our latest test of WordPress security plugins to see if they can protect against vulnerabilities, we found no plugins provided protection against a vulnerability when exploited through that editor. Further testing confirmed that two of the plugins that would likely provide protection against that type of vulnerability did when using the Classic editor. The other plugins that would likely to provide protection didn’t provide protection even with Classic editor, but further testing confirmed that it also fails to provide the same protection with the Gutenberg editor that it would provide when using the Classic editor.
The type of vulnerability used in the test is being found in WordPress plugins quite often recently. It is an authenticated persistent cross-site scripting (XSS) vulnerability caused by a lack of proper security handling of shortcode attributes. That would allow an attacker to cause arbitrary JavaScript code to run on frontend pages of the website. These are not a serious issue, since the attacker would need be able to generate content that includes a shortcode, which would normally require access to a WordPress account that can create a post. Making those of more a concern though is that we have been finding recently that developers are failing in attempts to fix those, as we found, for example, with a plugin with 200,000+ installs. [Read more]