16 Dec

No WordPress Security Plugin Prevented Exploitation of Unfixed Arbitrary File Upload Vulnerability in Popular Plugin

When it comes to the chances of vulnerabilities being exploited the reality is that many types of vulnerabilities are highly unlikely to have anyone even try to exploit them. Unfortunately far too often we see security companies and the press making a big deal of vulnerabilities that are are of little to no threat, while ignoring vulnerabilities and broader security issues that are leading to websites being hacked (that lead us to providing information on likelihood that a vulnerability is to be exploited to the data for our service). When it comes to types that are likely to be exploited, the arbitrary file upload vulnerability, which allows a hacker to upload files of any kind to a website, is probably the one with the most exploit attempts and also then ends up leading to the most websites being hacked. So if a WordPress security plugin is going to protect against any type of vulnerability this seems like this is the one you would most want it to be able protect against.

Back in September we tested out security plugins against this type of vulnerability and the results were not good. Of the 12 plugins tested only 3 provided any protection. The protections 2 of them provide was easily bypassed for this particular vulnerability and the remaining plugin’s protection also meant that Editor level and below users could not upload files either.

With the vulnerability tested then the file to be uploaded was included with the upload request, which provides security plugins a relatively easy way to detect the possibility of a malicious upload occurring as they can see all files being included in the request by checking the $_FILES variable. An arbitrary file upload vulnerability can also involve getting a file from another website, which should make it harder to detect.

Just such a vulnerability was disclosed in the plugin Delete All Comments (which recently had 30,000+ active installs according to wordpress.org) by the security company NinTechNet on Saturday, which they had discovered while cleaning up a website that had been hacked due to it. The vulnerability is just the type of thing that could show the value of a security plugin as the vulnerability has not been fixed, so even if you keep your plugins up to date at all times you are still vulnerable if you are using (WordPress could step in to provide a secured version, but so far they have not). So we decided to test out security plugins to see if they are able to protect against it.

Testing Procedure

For each of the tested plugin we set up a fresh install of WordPress 4.7, installed the version 2.0 of Delete All Comments, and installed the latest version of the security plugin. We tried to enable any feature of the plugin that could possibly have an impact on stopping exploitation of the vulnerability.

We used the following HTML to launch the upload request in the exploit attempts:

<form method="POST" action="http://[path to WordPress]">
<input type="text" name="restorefromfileURL" value="[URL of file to be upload]">
<input type="text" name="restorefromfileNAME" value="test.php">
<input type="submit">

The 15 plugins we tested include the security plugins listed in the Popular plugins section of the Plugin Directory and some others that look to intended to prevent this type of situation. We added three new plugins in this round of testing: Block Bad Queries (BBQ), Centrora Security, and Total Security. Followers of our blog might recognize two of those, as we previously disclosed a pair security vulnerabilities we found Centrora Security and Total Security (yes security plugins can introduce additional security issues on your website). If you would like to see an additional plugin included in future testing please leave a comment on the post or contact us.


None of the plugins tested prevented the vulnerability from being exploited.

We were surprised NinjaFirewall (WP Edition) didn’t prevent this since the developer was the one that discovered the vulnerability and they state that:

Alternatively, if your are using NinjaFirewall (WP/WP+ Edition), our WordPress WAF, you are protected against it.

One possible explanation for this discrepancy is that we sent the exploit attempt request to homepage of the website while the hack shown in their post had the request sent to /wp-content/plugins/delete-all-comments/delete-all-comments.php. When we sent the request to that URL instead it was blocked.

The full results are below:

Acunetix Secure WordPress

Result: Failed to prevent exploitation.

Acunetix WP Security

Result: Failed to prevent exploitation.

All In One WP Security & Firewall

Result: Failed to prevent exploitation.

Anti-Malware Security and Brute-Force Firewall

Result: Failed to prevent exploitation.

Block Bad Queries (BBQ)

Result: Failed to prevent exploitation.

BulletProof Security

Result: Failed to prevent exploitation.

Centrora Security

Result: Failed to prevent exploitation.

IP Geo Block

Result: Failed to prevent exploitation.

iThemes Security

Result: Failed to prevent exploitation.

NinjaFirewall (WP Edition)

Result: Failed to prevent exploitation.

Security Ninja

Result: Failed to prevent exploitation.

Shield WordPress Security

Result: Failed to prevent exploitation.

Sucuri Security

Result: Failed to prevent exploitation.

Total Security

Result: Failed to prevent exploitation.


Result: Failed to prevent exploitation.

Protecting Against Plugin Vulnerabilities

Seeing as the security plugins provided no protection, there are a number of other steps you can take to lessen the chances of being exploited through a vulnerability in a plugin:

  • Remove plugins that you are not planning to use anymore. Some vulnerabilities are exploitable even if the plugin is not activated, so just deactivating them will not fully protect you. In this case the vulnerability can exploited when not active if the request is sent directly to plugin’s file.
  • Keep your plugins up to date. Unless you are constantly checking for outdated plugins, your best bet is probably to enable WordPress’ ability to update them automatically. Our Automatic Plugin Updates plugin is one option for doing that.
  • Install our Plugin Vulnerabilities plugin. For vulnerabilities that it looks like a hacker is already exploiting, we include data on that in the plugin and you will get alerted to the situation even if you don’t use the service. We added this vulnerability on Monday.
  • Sign up for our service. Not only do you get alerted if there is a vulnerability in a currently installed version of a plugin, but we can also work with you to determine what is the best option for dealing with that situation. Maybe the vulnerability is something you can safely ignore or we can create a workaround to prevent exploitation until a proper fix is released. Your support of the service also help us to continue to work to get these types of vulnerabilities fixed.
  • Hire someone to do a security review done on the plugins you use. This is the most expensive option, but it also going to provide you the highest level of protection. It also will help everyone else using the same plugins. With our service you get a more limited version of this as you can suggest and vote for plugins to have basic security reviews done by us.
15 Dec

When a Security Company Does the Right Thing and The WordPress Plugin Directory Drops the Ball

Due to how bad the security industry is we rarely have the ability to point to a situation where the a security company has done the right thing, but today we have one to discuss.

Yesterday, we discussed how security companies rarely do one of the three basic components of a proper hack cleanup, which is to try to determine how the website was hacked. As we mentioned in that post, in instances where that isn’t done we are frequently brought in to re-clean the websites after they get hacked again. The problem of not determining how the websites are hacked doesn’t always just impact that website, if the vulnerability exploited exists in the current version of software on the website then spotting an early exploitation has the possibility of limiting the amount of additional websites that get hacked due to it. That possibility occurred with an arbitrary file upload vulnerability that exists in the WordPress plugin Delete All Comments. On November 20 the security company NinTechNet was looking into a hacked website and found the website was hacked due to that vulnerability. It wasn’t all that hard to spot with the combination of the logging and the code in the plugin, but since so many security companies don’t even try to determine how the websites they are cleaning up have  been hacked, something like that can easily get missed.

The vulnerable code was introduced in version 2.0, which was the first release put out by a new committer and that lead someone that mentioned the vulnerability to us, to believe this might have been intentional. To us it also looks like something that could have happened when someone writes code without having a good grasp of the security implications of what they wrote.

After NinTechNet spotted this they did the following:

The author was informed on November 20th but did not respond. We contacted the WordPress plugin department and the plugin was removed from the repository the same day.

On Saturday they publicly disclosed the vulnerability. Subsequent to that we added it to the service’s data and added it to the free data that comes with the service’s companion plugin on Monday, so even those not using the service yet could have gotten notified of the issue (if you haven’t installed the plugin, now would be a good time to do that).

Looking at the logging from our websites and the third-party data we monitor we don’t see any evidence of wide scale attempt to exploit this until Monday. So between when NinTechNet came across this and that there was a chance for the WordPress Plugin Directory to mitigate the threat from this when the developer didn’t.

The easier thing they could do is to start warning people when they are using vulnerable plugins that have been removed from the Plugin Directory, but they are refusing to do that on the basis that it puts people at more risk. As we discussed before that doesn’t make much sense as hackers can still figure out that the vulnerabilities exist even if they keep quiet about it.

The other option would be for them to put out a new secured version of the plugin, which they have the ability to do. They even have the ability to have the update to that version of the plugin happen automatically, in the same way that minor WordPress updates now occur automatically (and in the same way all plugin updates can happen with our Automatic Plugin Updates plugin). Like a lot of security related items involving the Plugin Directory, the process for deciding to release a secured version is rather opaque. In one instance when we tried to raise the issue over the lack of this happening on the wordpress.org Support Forum our post was deleted without explanation and the plugin being discussed was never fixed. If they decide to improve the situation we would love to help with it.

Instead they did neither, leaving everyone using the plugin vulnerable.

Until WordPress gets better about this you can help protect your website for free by installing the service’s companion plugin and installing one of our other plugins that lists plugin you are using plugins that have been removed from the Plugin Directory. For those with the budget you can sign up for our service, where you get data on all plugin vulnerabilities, not just ones that are already being exploited, and you also have the ability to suggest and vote for plugins to have a security review done by us, which could help catch more security vulnerabilities in plugins before they have a chance to be exploited by hackers.