Hijacked WordPress.com Accounts Being Used To Infect Sites

Update on May 23 at 11:50AM: A representative from WordPress.com reached out to us with the following statement:

There has been some misinformation making the rounds, so to clarify, there has been no security breach for user accounts at WordPress.com. But if someone else has your WordPress.com account credentials, they could log in and modify your site.

WordFence notified us of a malicious plugin being installed on some accounts, so we are investigating and will be in touch with those account owners. We’ll also take steps to ensure that none of our users accidentally install that plugin.

In the meantime, we encourage all users to pick a strong password and use 2FA. https://en.support.wordpress.com/selecting-a-strong-password/

–End of update. Original post follows.

Our customer service team raised the alarm about a problem several users have had in the last few days. They all reported a malicious plugin named “pluginsamonsters” suddenly installed on their site. They learned about the problem thanks to an alert from Wordfence.

Our team has investigated these compromises and in this post we will describe how the attackers are gaining access and what you can do to prevent it from happening to you.

High Level Summary

In summary what is happening is the following:

  1. An attacker will sign in to a WordPress.com account using compromised credentials.
  2. If that account on WordPress.com is set up to manage any WordPress.org WordPress installations via the Jetpack plugin, the attacker will use that access to install a malicious “pluginsamonsters” plugin on the target site.
  3. The plugin gives the attacker full control of the target website and the site is now compromised. The plugin is visible on the WordPress.com dashboard but is invisible on the target WordPress site’s plugin list when active. (It is visible when deactivated)

For this attack to occur, the following conditions need to be met:

  1. The site owner must have Jetpack installed.
  2. Jetpack must be configured to allow the site to be managed from a WordPress.com account.
  3. The WordPress.com account must have compromised credentials. This usually happens when you have reused an email/password combination on another site or service that has been compromised.
  4. The WordPress.com account must not have two factor authentication enabled.

Weak WordPress.com Credentials And Jetpack as Entry Vector

Jetpack is a popular WordPress plugin with a range of features, including the ability to integrate with WordPress.com. In order to use Jetpack, you have to create an account with WordPress.com. It allows you to manage multiple WordPress sites from one central console at WordPress.com. One of the features available is to manage plugins on your sites, or even install new plugins.

Just as in WordPress installed on your server, you’re able to either select a plugin from the WordPress public repository, or upload your own plugin in a zip file:

When Jetpack is connected to your site, it has the same privileges as the site administrator account. So if you choose to upload a plugin, whatever you upload will be passed along and installed on your site, no questions asked.

As we investigated the sites with “pluginsamonsters” installed, we found signs that this feature is being abused. For example, we checked site access logs at the time the plugin was created (per the timestamp on its directory), and found entries like this: - - [22/May/2018:02:38:06 +0000]
"POST /wp-admin/admin-ajax.php?token=[redacted]&timestamp=1526956686&nonce=uFn5aA
yBXc%3D HTTP/1.0" 200 141 "-" "Jetpack by WordPress.com"

The source IP address is part of Automattic’s network, the authors of Jetpack. We also worked to identify plugins that all the affected sites had in common, and Jetpack was the only one. Once our lead developer pointed out that Jetpack allows for remote installation of a plugin, the pieces fell into place.

We connected Jetpack on some of our test sites and tried to upload a malicious plugin. It worked, and our access logs showed the same activity.

Pluginsamonsters malware

Our next step was to analyze the malware and find out what it’s doing. This didn’t take long – it’s fairly simple, and as we mentioned, it’s a variation on malware we’ve seen before. Much like its relatives, it hides itself from the list of plugins in a site’s WordPress dashboard. To be clear, the plugin is still visible on the management console of WordPress.com, but is hidden on the admin interface of the victim website when it is activated. The plugin is visible on the victim website when it is deactivated.

The malicious plugin maintains a “.txt” file that can contain code to be executed on the WordPress loop_start action. It also includes a separate PHP script which is a simple file upload tool.

We were able to observe the hackers’ use of this tool. They’re using it for two purposes. First, they’re adding more backdoors to infected sites in order to maintain access. These backdoors are also simple file upload tools, and they’re being created with innocuous names like wpcfgdata.php, wpplugdata.php, etc. Second, they’re altering the root index.php file of the infected sites. This is the real reason for the campaign, the part that’s making profit for the hackers.

The malicious code added to index.php is obfuscated, but fairly simple. It reaches out to a malicious domain – in all our samples, it was roi777[dot]com. From that domain, it gets another malicious domain – we observed dozens of these, all in the “.tk” TLD. It uses Javascript to redirect visitors to a page on the second malicious domain, and sets a cookie so that the redirect only happens once every 12 hours.

The following is a screenshot showing the obfuscated code added to index.php.

In our tests so far, the malicious pages to which visitors were directed contained scareware, complete with text-to-speech, popups, and mouse hijacking:

But there may be other content served based on the device, source IP address, and so on. On infected sites, the “.tk” domains are refreshed once every minute.

In some cases, the attackers are also editing core Javascript files, infecting them with code to produce popups when visitors click anything in the site. They seem to be targeting jQuery files located in /wp-includes/js/jquery.

The first instance of this attack we observed was on May 16. Starting yesterday, May 21, the attackers started installing the same malicious plugin under a different name, “wpsmilepack.”

How Attackers Are Getting In

We observed these same attackers using “credential stuffing” attacks in February. They were taking stolen usernames and passwords from data breaches and trying to use them to log in to WordPress sites directly, even going so far as to check domain registration records for sites registered to a compromised email address. In response, we updated Wordfence to prevent logins using compromised passwords.

These attackers are resourceful, and it looks like the Jetpack angle is just the latest they’ve found to try. It further demonstrates how dangerous it can be to reuse passwords across services.

What You Can Do

To protect yourself from this attack, we recommend you take the following actions:

Taking these steps will lock down your WordPress.com account and ensure that attackers can’t use it as an entry vector into the sites that you manage.

Centralized Management Services As A Target

WordPress.com gives you the ability to remotely manage multiple sites via the Jetpack plugin. This kind of functionality is provided by several other services. This can be a powerful enabler for agencies and developers who manage large numbers of WordPress websites. Let’s face it, updating hundreds of websites is not fun and anything that makes it easier is a valuable service.

It is important to realize that, while remote management tools are powerful enablers, they also have administrative level access to the sites that they manage. As a user, it is your responsibility to ensure that your user account uses a strong and unique password along with two factor authentication. If not, you risk mass compromise of all sites managed by a service like this.

These compromises we are reporting today are not the result of a vulnerability. They are the result of site owners reusing credentials. As the old saying goes: “There are no victims. Only volunteers.” In this case if you reuse credentials on a management level account and don’t have two factor authentication enabled, you are volunteering to have a bad week.

Wordfence Free Detects This Malware Variant

If you have been hit by this attack, our site cleaning team can resolve the compromised site quickly and effectively. You can find out more about Wordfence site cleanings on this page.

In all cases, customers with compromised sites discovered they were hacked because the Wordfence malware scan picked up on the malicious code the attacker had installed. Because this is a variant of older malware we have been tracking, both our free and Premium scans can detect the malware the attacker is installing. So to protect yourself against this, simply install the free version of Wordfence and it will alert you if a variant of this malicious plugin is detected.

We have been recommending Troy Hunt’s “HaveIBeenPwned” service for some time now. I had the pleasure of meeting with Troy a few weeks ago in Redmond. Once again we are recommending you use HaveIBeenPwned to check if your email address has been involved in previous data breaches. If it has, ensure that you change your password on all services you use. Use a strong and unique password on each service and use a password manager like 1Password to manage your strong unique passwords.

Wordfence has integrated the HaveIBeenPwned database to ensure that you don’t use breached passwords for your WordPress accounts. We don’t have control over the user account that you use for WordPress.com so you will need to manually ensure that you are not using a breached password for that account.

As always we very much appreciate your comments and questions. Please post below and I’ll be around to answer them.

Written by Brad Haas and Mark Maunder with research by Åsa Roseberg and James Yokobosky. Technical editing by Matt Barry. Final editing by Dan Moen. Special thanks to Åsa, James, Matt and Brad for the primary research that resulted in this publication.  

PS: No businessmen were harmed during the production of the stock photo used in this blog post.

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  • Brilliant diagnosis and remedy.
    This is why I use WordFence on all of my client accounts.

  • "PS: No businessmen were harmed during the production of the stock photo used in this blog post." Funny. :)

    Thank you for the information. You and your team are very appreciated.

    Donna :)

    • Was wondering if anyone would stay for the credits. ;-)

  • Awesome research and writeup. My site was infected and everytime I manually cleaned it up it kept being reinfected and any visit redirected me to a scareware site. Until I installed WordFence.

  • Thanks for the heads up. One of my sites was infected with three plugins "pluginsamonsters", "pluginmonsters", and "ls-oembed". Updated passwords and my host is helping with scanning and restoring my site.

    • Glad to hear we helped.

  • I had a temporary Wordpress site for a design class for college. It was hosted with siteground. I have been receiving multiple emails from jetpack daily because the hosting has expired and it’s reporting my site is up then down. How can I eliminate this problem? I can’t access the site any longer since the hosting has expired. I don’t want it to infect my real Wordpress website. Thank you

  • Thanks so much! No infection on my site. Quick and easy fix. I feel protected now!

  • I logged onto my Wordpress.com account and went to the Plugins page, but I can't see a list of the plugins that are installed on my sites. Up at the top, I see the search bar magnifying glass and the Upload Plugin button, but I don't see the gear labeled Manage Plugins that's shown in the image at the top of this article. I thought that would be a good way of checking to see if any of the rogue plugins were installed.

  • Never mind, I figured it out. I had to switch to an All My Sites view.

  • This is exactly why I wish the powers that be weren't trying to shove Jetpack down our throats with all of the site notification promos and gazillions of options. Jetpack ... jack of all trades, master of some. I understand the need to monetize, but it has gotten so spammy that it is a real turnoff. Automatic used to respects its users better than this.

  • Hello,
    I entered my email address into the recommended haveibeenpwned site and it returned:
    Oh no — pwned!
    Pwned on 3 breached sites and found no pastes (subscribe to search sensitive breaches)

    I checked wordpress.com plugins for any extra plugins installed and there were none. Wordfence is not indicating any malicious activity on any of my sites.

    Why does the haveibeenpwned site say I have 3 breached sites?

    I should note: A few years ago I had a single site that was compromised, but not 3 of them?

    Thanks for your help,

    • Not three breached sites. It means you have used three services where your credentials have been leaked. For example, if you used Adobe and they got hacked, that's one service.

  • My site was infected with this and the free Wordfence scan picked it up. The service that Wordfence provide to clean up your site is excellent. It has really brought home the importance to me of password security and 2step authenication

    • I'm really glad we could help Caroline. Thanks for that feedback!!

  • One of my sites installed on Wordpress.com started spamming others with short comments like "wow" or "what?". I don't know how to check if this is the case of hijacked Jetpack credentials. How to check the site/plugins which are located on Wordpress.com?

    • If the site is sending those comments with no human interaction, I'd say there is a very good chance that it is compromised though there is no way to be certain if it was from one compromise or another without looking at the site. There are some good guides on how to clean your site with the Wordfence plugin (Free and Premium) available here and here. I think we have mentioned before that if you are using the Jetpack connect feature to login, using the 2 Factor authentication option is important as an additional level of protection.

      Thanks and stay safe!

  • Hi Mark,

    My website had a DDoS attack about a week ago. During that time one of the errors that came up when trying to bring up a page mentioned a plugin that I didn't install.

    I don't see any issues now and I don't see any plugin on my site or in the wordpress.com account. The site has also been scanned by my host and wordpress "high sensitivity" and it didn't note any changes. (I had the free version of Wordfence installed at the time and used Cloudflare to mitigate the attack.)

    Do you think I need to also get my site "cleaned" by Wordfence or do things sound OK? I just don't want any backdoor/"sleeper" surprises later. Thank you.

    • That's hard to say without looking at the site. Running a scan with all the scan options enabled and watching the results to see if there was anything strange would be a good first step. You can also use this guide in our free learning center to help you determine if you were in fact compromised. There are some good guides on how to clean your site with the Wordfence plugin (Free and Premium) available here and here. And, of course, you are always welcome to reach out to our SST pro team for a site cleaning if you need help.

      Thanks and stay safe!

  • Who would use WordPress.com to log in to their Self Hosted website? That is just stupid.
    Self Hosted WordPress developers should be distancing themselves from wp.COM as much as possible. It's bad enough we have to explain the difference between the Fake wp.COM site and Real wp.ORG self hosted websites.

    For that matter, who would use JetPack, it's terrible. It slows down your site and causes all kinds of issues.

    I've been a developer for 15 years I would never use JetPack or allow a client to use WordPress.com to log in to their self hoseted website.

  • The best post possible .Makes it even more important to have good and secure password for wp account.

  • Hi Paula,

    You can contact Jetpack support via https://jetpack.com/contact-support/ and include the ID number that in the footer of the outage e-mail. Jetpack support can fully disassociate that site and stop the notices.

  • The site I am talking about is on wordpress.com with free plan so I am not able to install plugins. There is only Jetpack installed there. I have set two factor authentication but comments are still sent to people without my knowledge.

    • This affects wordpress.org self-hosted sites that are managed via wordpress.com and jetpack. So you are not affected if your site is on WordPress.com.

  • As for the update to your article and WP representative statement: "pick a strong password and use 2FA". I followed this advice but still someone posts comments using my gravatar and the address of my site. I am on free basic plan with JetPack as the only pre-installed plugin on wordpress.com and with the theme chosen from the WP gallery (Grisaille). There is nothing risky I would install by myself because on a free plan I am not allowed to do this. Today I disabled pingbacks and trackbacks on the main page to see if that helps.