Let’s start by saying that if you’re concerned about WordPress XSS, you’re being cautious rather than crazy. The cross-site scripting vulnerability isn’t limited to WordPress websites, but it does affect them all. Installing a firewall and keeping your themes and plugins up to date are the best defences.
We’ll lay down what the vulnerability is in detail in this article—be patient, it’ll become technical—so you can make informed decisions about your website’s security. We also have a comprehensive tutorial on how to avoid assaults that you should read.
TL;DR: If you believe that your WordPress site has been hacked, we recommend installing MalCare right away to remove the infection.
What is WordPress XSS?
WordPress XSS is a malware attack that uses a cross-site scripting vulnerability on the WordPress website to carry out the attack. It’s the most common way for WordPress sites to be hacked, especially because there are so many plugins with XSS flaws.
So what is cross-site scripting?
There are many different forms of attacks, however for the sake of clarity, they can be divided into two categories:
The malicious script is run on the client-side in the browser; or one in which the malicious scripts are saved and executed on the server before being served by the browser;
In any situation, the hacker can employ an XSS attack to steal data or alter the appearance and behaviour of the site.
This is a simplified cross-site scripting method. A more complete explanation can be found towards the end of this article.
Why are XSS attacks so common?
WordPress plugins can be quite difficult to understand. Sometimes it’s even more complicated than WordPress. The likelihood of security concerns increases as the complexity of the system grows. XSS assaults are very tough to defend against, making the plugin author’s task even more challenging.
Even the top web corporations with specialised security teams, such as Google, Apple, Facebook, and others, have been targeted. It will help put things into perspective in terms of how it could infiltrate a WordPress plugin with far fewer resources.
Is my website vulnerable to an XSS attack?
If you use a firewall and keep everything up to date, the chances are much smaller. But keep in mind that there is no foolproof defence against such attacks. A hacker may be able to take advantage of a non-public vulnerability. As a precaution, monitor your website on a frequent basis.
While the extent of the harm caused by such flaws varies depending on the specifics of the problem, in the worst-case scenario, hackers might seize control of the entire website. In certain situations, hackers may be able to make minor changes to the site, or even reroute your traffic to their own malicious site.
In other words, hackers can exploit your browser to do the following things:
- By sniffing out the Session ID, you can hijack a user’s session.
- Place unlawful pop-ups and redirects on your website.
- Carry out phishing attacks
- Install keyloggers that record the victim’s every keystroke.
- Financial information is stolen.
There is only one way to protect yourself from such attacks. Install MalCare’s firewall as soon as possible.
Are all XSS attacks equally dangerous?
No, it’s not true. Some XSS attacks are far more hazardous, as they can grant the hacker entire control over your website. Hackers can then take over the site and do anything they want with it.
Others just allowed the hackers to change a limited piece of the website. This, too, can be quite dangerous, as malware may be sent to your visitors, among other things.
Some XSS attacks need the hacker to already be a site contributor. In this instance, the risk is significantly reduced.
How do hackers exploit such vulnerabilities?
To find vulnerabilities, the majority of hackers employ automation. After then, it’s simply a matter of putting the hack into action. In some circumstances, a bot can carry out the full attack.
We already taught you that there are five primary ways for a hacker to exploit cross-site scripting in a realistic way. Let’s go over each of those options one by one.
Hijacking the user’s session
We’ve already discussed how an XSS attack can access a cookie. The most dangerous aspect of being able to retrieve a cookie now is that the same attack can also reveal a user’s session ID.
Sessions are used by most websites as a unique identifier for each user. Session cookies are used to keep track of these sessions. Using a simple script such as this:
The session cookie can be sent to the site http://192.168.149.128/ by a hacker. This request is recorded in the server’s access.log file.
The hacker can now easily log into each account you’ve ever signed into using this session information without ever having a password.
Perform unauthorised activities
This type of attack can take the form of a defaced website or a malicious script that spreads to an increasing number of people.
In many cases, a WordPress XSS attack is just the beginning of a much bigger strategy. Cross-site scripting might also lead to phishing attempts on your website. Most of the time, the malicious script will launch phishing schemes on your site, tricking your visitors into handing up critical information.
If you’d like to learn more about phishing assaults, we have a comprehensive essay on the subject.
The hacker uses a script to instal a keylogger on a vulnerable site in this attack scenario. Every time a user writes something into the keyboard, the keylogger records it and sends it to the hacker. This is a risky assault that can quickly capture passwords and credit card information.
Stealing Sensitive Information
Cookies and how they can be taken have previously been discussed extensively. This form of attack just expands on the same idea.
Assume your bank’s internet banking page is vulnerable to cross-site scripting (XSS) assaults. The hacker might easily enter into your bank account without any validation using the right script!
This isn’t a brand-new concept. It’s basically a more advanced use of session cookies by a hacker.
How can you protect yourself from XSS attacks?
In the face of a continuously changing threat, firewalls are your best defence.
Special rules in firewalls monitor for requests that may contain strange content, such as that found in XSS attacks. The difficulty is that hackers are constantly coming up with new and improved versions of this destructive language that can get past even the most sophisticated firewalls.
However, this is not always the best option. It’s a cat and mouse game that frequently yields false positives.
You should absolutely read our post on how to safeguard a WordPress site.
How to detect a WordPress XSS attack on your site
Installing a security plugin like MalCare is the simplest way to detect an XSS attack on your site. Every day, MalCare’s automated malware scanner examines your entire site. The malware scanner finds harmful scripts anywhere on your site using a cutting-edge machine learning technique.
MalCare can even detect unknown malware and clean it for you using the ‘Autoclean’ feature.
Of course, the prudent thing to do is to avoid allowing such a breach to occur in the first place. However, XSS assaults are extremely difficult to defend against. The best you can do is improve the security of your WordPress installation.
You can also use MalCare’s Advanced Firewall to protect yourself. MalCare’s firewall blocks suspicious or malicious IP addresses from connecting to your site automatically.
What’s the best part? When a hacker’s IP address is identified on one of MalCare’s 250,000+ protected sites, that IP address is blacklisted from all MalCare-protected sites.
Don’t worry if a member of your team or the website administrator’s IP address is mistakenly prohibited from accessing the site. See how to whitelist an IP address in our tutorial.
How does XSS work?
This data input field is no longer required to be a visible field. It could even be a bug in your site’s code that retrieves unclean data from any file or database.
XSS attacks were also possible in the WordPress core. To execute XSS, all a hacker had to do at first was generate a PHP file with the following lines of code in it:
/* Template Name: <script>confirm(document.cookie);</script> */
That piece of code is just a comment that declares the file’s name. On its own, it’s benign and gets ignored by WordPress.
The template name would have been fetched by the WordPress Theme Editor as is in an older version of WordPress, therefore it would have been executed instantly. The template name was retrieved by the Theme Editor using the ‘$file description’ function, which was vulnerable to XSS attacks.
Naturally, the script in the above example isn’t particularly powerful or malevolent. The point, though, remains the same. Malicious code can be executed in any input field if benign code can!
The vulnerability was patched in WordPress version 4.8.2, although it is present in many WordPress themes and plugins.
In reality, many WordPress plugins suffer from this issue. The truth is that most plugins are really complicated. Some are even more complicated than the basic WordPress files. This level of intricacy frequently leads to security concerns.
That’s how XSS in WordPress works. If you’re using an older version of WordPress, we strongly advise you to update right away.
A list of WordPress plugins with known XSS vulnerabilities may also be found here. We strongly advise you to stay away from them as much as possible. Whether you’re using one of these plugins, see if there’s an update available that fixes the flaw and brings you up to date.
Types of Cross-Site Scripting
There are two sorts of XSS attacks that you should be aware of:
The visitor to your website is the subject of a stored or persistent XSS attack. Customers are defrauded, and their personal information and finances are stolen.
The target of a reflective or non-persistent XSS attack is your WordPress website.
We’ll go over both attacks in great depth.
Stored Or Persistent XSS Attack
Assume your website is a blog where visitors can leave comments on the items you publish. The data is delivered to the database and stored when a visitor writes a comment.
Before data is transmitted to the database, your site should have configurations to cleanse it. This implies it should determine whether the user’s input is a legitimate comment or a malicious script. It opens up a WordPress XSS bug if these checks aren’t in place. Let’s have a look at how:
Step 1: Hacker Finds The Vulnerability And Exploits It
Automated scanners are used by hackers to search the internet for websites that contain an XSS vulnerability. They locate your website and insert dangerous code into your comment section. Your website accepts the script and sends it to the database because it has no checks in place.
Step 2: A Visitor Views The Infected Page
The hacker’s input would seem to a visitor as a normal comment. What the visitor and website owner don’t realise is that this comment is actually a piece of executable code meant to steal cookies. This page will affect anyone who simply visits it.
Step 3: The Hacker Steals Browser Cookies
We know that most people have many tabs open in their browser, including email, Facebook, a shopping site like Amazon, a work website, YouTube, and so on.
The code is run when they visit your website and view the page with the hacker’s comment. The hacker will be able to grab their browser cookies as a result of this. Because they can steal cookies from all sites open in separate tabs, this assault is known as a “cross-site” attack.
Step 4: The Hacker Exploits The Stolen Cookies
Hackers can then use these cookies to impersonate authenticated users on the shopping site and make transactions. The attackers have the ability to obtain sensitive account information including usernames and passwords. They can also gain access to your email account and send phishing or fraudulent emails to your contacts. The list goes on and on.
Anyone who visits your website is put at risk by this type of attack. The next form of XSS attack is one that directly targets the website.
Reflective Or Non-Persistent XSS Attack
We witnessed how hackers target visitors in the previous attack. Hackers, on the other hand, infect the website itself in this attack. As previously stated, the majority of internet users have many tabs open on their browsers.
The same can be said for website proprietors.
Your WordPress admin user dashboard is frequently only one of the tabs open in your browser. This opens the door to a reflecting XSS attack.
We’ll show you how this works:
Step 1: Getting the Site Owner to Click on a Malicious Link
Hackers frequently distribute harmful links through emails, hoping that someone will fall for their ruse. Hackers may also include these malicious URLs on other WordPress sites.
When you click the link, a script from an external website is loaded on your website. This link has the following code:
Step 2: Grab Session Cookies
The code is executed when you click on the link. This allows hackers to steal your cookies and impersonate a user who is logged into your WordPress site’s administrator account. They could steal login passwords and sensitive data, lock you out of your own website, and use it to carry out other hacks if they have access to it.
XSS attacks can have serious effects for your website and business. It takes a long time and a lot of money to recover from such an attack. By taking safeguards against XSS, you can prevent becoming a victim.
So, what’s next?
The next step is to put in place safeguards against future assaults. There’s no polite way to say it, but there’s no failsafe solution to keep your website safe from cybercriminals. For the time being, the best we can recommend is establishing a strategy for doing regular WordPress security audits.
We have a whole post dedicated to preventing XSS attacks in WordPress. So, if your site is now being attacked, we urge that you go to that article and read it.
MalCare is also available for download right now. It takes care of the majority of the grunt work required to increase your site’s security.