Over at our Plugin Vulnerabilities service we are in the process of trying to help to get a fairly serious security issue with a WordPress plugin fixed. In the process of doing that we have noticed an issue with WordPress that impacts more than this plugin. Without getting into the details of it, since a fix is still in progress, the plugin created WordPress pages which provide access to non-public data. These were accessible by the public, which was a problem. As part of trying to fix this, these pages were intended to be made private (we say intended because that wasn’t done right). This would have worked in private pages were totally private, but it turns on they are not.
Here is how the WordPress documentation describes what the impact of setting a post’s or page’s visibility to private:
Private content is published only for your eyes, or the eyes of only those with authorization permission levels to see private content. Normal users and visitors will not be aware of private content. It will not appear in the article lists. If a visitor were to guess the URL for your private post, they would still not be able to see your content. You will only see the private content when you are logged into your WordPress blog.
Despite the claim that “normal users and visitors will not be aware of private content”, that isn’t totally true. If you have your permalink structure set to include the title of the page in it, which is fairly common set up, then someone can find out the titles of private posts and pages.
You do that by taking advantage of WordPress’ automatic redirection from plain URLs to the chosen permalink structure. Lets say a post with ID number 12 was titled Surprise Party For Julie In Accounting, when accessing
http://example.com/?p=12
WordPress to automatically redirects you to
http://example.com/surprise-party-for-julie-in-accounting/
The page you see though gives no indication that a private page exists, as the documentation suggest:
By enumerating through potential ID numbers you can see what the titles of all private posts and pages on a website are.
Coming back to the plugin, the title of those pages contains enough information to allow some access the non-public data. While the plugin shouldn’t have you used pages in the way it did, we suspect that in other cases private posts or pages could also contain sensitive information in the title that isn’t meant to be public, as it is now.
After noticing this we thought that we should bring this to the attention of the WordPress developers since it doesn’t seem like this should be this way. It turns out that someone already did that 8 years ago, back around the time of WordPress 2.3.1. But 7 years ago that ticket was closed and marked as “wontfix”. Maybe there was some good reason for that, but the only comment included with that change was “there’s a dup of this one somewhere, and it shoud get wontfixed too.” The fact that a potential security issue was treated in this way is more than a little concerning.