Shortcode Injection Vulnerability
Ultimate Member versions older than 1.3.84 allow unauthenticated users to execute arbitrary WordPress shortcodes via AJAX. The vulnerable code exists as far back as version 1.0.0 when the plugin was first published. If you are using any version of this plugin, update immediately. At this time, the plugin revision notes do not address this vulnerability nor has the developer released any information related to this issue.
The default WordPress shortcodes are relatively secure but other installed plugins often include insecure shortcodes, including the Ultimate Member plugin. Some of the Ultimate Member shortcodes are documented at http://docs.ultimatemember.com/article/210-ultimate-member-shortcodes.
Executing arbitrary shortcodes
Ultimate Member adds the ‘ultimatemember_frontend_modal’ AJAX action which is accessible to anyone whether they are logged in or not. This allows passing arbitrary arguments to the do_shortcode() function and returns the results.
Include arbitrary PHP files
Using directory traversal and the ‘ultimatemember_account’ shortcode PHP files accessible on the host can be included. The following function is what is called when the ‘ultimatemember_account’ shortcode is executed.
Adding a template argument to the shortcode allows the PHP file to be included.
For example the following shortcode call allows viewing some user stats from the dashboard:
If a method could be discovered that allows uploading arbitrary PHP code, this could be used to execute that code.
- 2/27/2017 Notified developer of issue
- 3/9/2017 Second notification to developer
- 3/10/2017 ‘Clean up’ commit on GitHub
- 3/10/2017 Developer reply saying they removed the offending code
- 4/17/2017 5:30AM PST Version 1.3.84 tagged in GitHub
- 4/17/2017 6:34PM PST Version 1.3.84 released on wordpress.org
Back in March 2016 Ninja Forms version 3.0 started to roll out, there was an unknown vulnerability at the time that allowed unauthenticated end users to inject arbitrary WordPress shortcodes via form field submissions. The issue was resolved in version 3.0.31.
The default WordPress shortcodes do not provide much further access and accessing the [ninja-forms] shortcode would only allow an attacker to preview un-published forms. While these shortcodes could allow leverage for further attacks by default this is a very minor issue, though if a site has additional plugins installed that provide shortcodes then this vulnerability could be leveraged to execute those.
- 10/27/2016 First contact to vendor regarding issue
- 10/27/2016 Received vendor support reply saying they will forward on the issue
- 11/9/2016 Version 3.0.15 released
- 11/10/2016 Second contact regarding issue
- 11/21/2016 Version 3.0.16 released
- 11/22/2016 Third contact regarding issue
- 12/6/2016 Version 3.0.18 released
- 2/28/2016 Version 3.0.30 released
- 3/2/2017 Fourth attempt regarding issue
- 3/3/2017 Reply from developer saying they see the issue and will be resolved
- 3/7/2017 Version 3.0.31 released
Ultimate Member versions less than 1.3.76 contain a critical security issue that allows unauthenticated users to reset any users password to an arbitrary value. This could allow an external attacker to take over an Administrator account and completely compromise the WordPress website. The WordPress.org repository claims there are 40,000+ active installs of this plugin, though there is no way of knowing how many are running vulnerable versions.
If you are running an older version, upgrade immediately. This flaw exists as far back as 1.0.0, which was the initial release of the plugin. The change log for the plugin doesn’t mention the specific flaw and
at this time I have not seen an announcement from the Ultimate Member developer. On December 8th, the developer published a blog post and a twitter post regarding the issue.
Due to the severity of this vulnerability, I will not provide specific details of the vulnerability at this time.
- 11/22/2016 12:00pm Sent vulnerability information to vendor
- 11/23/2016 3:40am Vendor replied saying issue was resolved with github commit b66c99b
- 11/23/2016 8:45am Sent followup to vendor explaining additional vulnerability
- 11/28/2016 4:52am Received vendor response saying additional fix was added with github commit c54e8d3
- 11/28/2016 Ultimate Member version 1.3.76 released