Introduction to XSS Attack
Cross-site Scripting (XSS) attacks have been around for almost as Long as there have been web applications that assist website owners in building dynamic, useful websites. But even though the first XSS attacks were discovered in the 1990s, cross-site scripting is still a problem today, well into the twenty-first century.
Today, we'll examine cross-site scripting to learn what it does, why hackers adore it, and why website owners find it difficult to eradicate.
The State of Cybersecurity
Perhaps the responsibility issue is where the issue first arises. You could make the case that in the twenty-first century, even inexperienced users need to be aware of the main online dangers that exist today. If they click on a dubious link and their data is stolen, you might even go so far as to say that they are solely to blame.
Every website owner should treat their users' data with the utmost respect. However, the state of cybersecurity today demonstrates that this isn't really the case. Every day, successful attacks on websites are reported, and the cybercrime scene is continuing to grow.
More than 72% of all cyberattacks target websites in 2019, and of those, more than 40% attempt to exploit cross-site scripting vulnerabilities, according to a PreciseSecurity survey. According to PreciseSecurity, XSS attacks are the hackers' go-to tactic.
What is Cross-Site Scripting?
A cross-site scripting attack is clever because it operates on the user's device. In essence, the hacker transports a malicious script to the user's computer using a vulnerable website. The browser executes the script without question because it is from a legitimate website.
Because of how long the threat has existed, hackers are very skilled at checking potential targets for XSS vulnerabilities. While an attack can be planned on a budget, the potential rewards are enormous.
For instance, JavaScript-based XSS makes it possible to deface websites because the malicious script can change the content that the browser displays. In more extreme situations, attackers may change a press release or the documentation for a product in order to harm the reputation of the business.
XSS attacks typically target users and their data, though.
Even though JavaScript runs in a comparatively secure environment, malicious JS scripts can access the victim's microphone, camera, and geolocation by using HTML5 APIs. It can also initiate HTTP requests to arbitrary domains, potentially infecting the victim's system with malware.
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XSS attacks are also used by hackers to hijack sessions and take control of accounts. The website data that the browser has saved is accessible to JavaScript. This includes session token-containing cookies, which save you from having to enter your username and password each time a server request is made by keeping you logged into your account.
Hackers can impersonate you using the session token without knowing your login information. From that point on, taking control of the entire account is simple.
Types of Cross-Site Scripting
As usual, when launching an XSS attack, hackers have a wide variety of attack vectors to pick from.
Sometimes they manipulate users into clicking on a fake link or going to a specific URL by using social engineering and spam. In other cases, they take over the web application and wait for users to swarm so they can unintentionally run the malicious scripts.
There are three different kinds of cross-site scripting that you can identify depending on the setup and phases the attack goes through during its execution:
- Attacks using stored XSS
Blind XSS refers to a subset of stored XSS attacks. A blind XSS attack differs from a typical persistent XSS attack in that the goal of the attackers is to run the payload in the web application's backend. In other words, rather than the users, it's typically directed at the site administrator.
- Reflective XSS attacks
Reflective XSS attacks, also referred to as Type 2 or non-persistent XSS attacks, don't involve the attackers storing the payload in the infrastructure of the application. It is instead returned from the web server in response to a carefully constructed request.
Reflective XSS vulnerabilities affect a much larger number of websites, and this kind of attack is much more frequent. Successful reflective attacks typically involve some kind of social engineering and don't impact all users, in contrast to stored cross-site scripting.
- DOM-based XSS attacks
The user clicking an attacker-made link is another requirement for DOM-based XSS attacks.
The malicious URL contains the payload, which is then passed to the Document Object Model (DOM) of the browser and executed there. Because the browser believes the request is coming from the web application, this occurs.
The worst thing about DOM-based XSS is that traditional XSS defences don't protect against this kind of attack. Vendors of browsers have attempted to implement XSS protection mechanisms over the years, but their success has been patchy.
The only way to keep users safe, particularly from DOM-based attacks, is to adhere to some best practises when creating your website or app.
What to Do in Case of Cross-Site Scripting?
It is very challenging for users to recognise a cross-site scripting attack. The XSS operation is typically covert, and the victims rarely become aware of the attack until their account has already been compromised.
Even worse, a persistent XSS attack can start just by visiting a website that appears to be helpful. Nevertheless, you can create a secure environment by making sure your browser is current and by using only reliable security software.
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The standard security best practises still apply when dealing with XSS attacks brought on by maliciously crafted URLs: use extreme caution when clicking links and treat everything with a grain of salt.
It is your responsibility as the website owner to make sure that malicious links and weak web applications are as scarce as possible. Here are some of the most critical factors to consider:
1. Write secure code.
The initial design of the app is where it all begins. Online tutorials are available to assist you in creating an application that processes user input more securely and enables you to improve your defences against cross-site scripting right away.
2. Run regular security audits.
Even if you adhere to every coding best practise, a minor error made during core development or an update may unintentionally introduce an XSS vulnerability. Regularly checking the app for security flaws will help you find the bug early on and fix it before it causes any real problems.
3. Install all available updates.
Open-source content management systems like WordPress are the foundation of the majority of active websites. Using them increases your chance of defending your website against XSS because a large online community is dedicated to finding and fixing security flaws for you. Of course, it's still your responsibility to make sure that all updates and security patches are applied as soon as possible.
4. Set up a web application firewall.
The above steps must still be carried out even with a web application firewall (WAF) that has been set up properly. However, such a tool can spot and stop activity that appears to be a cross-site scripting attack, adding an extra layer of security to your website.
The Function of Your Hosting The provider
Nobody wants an XSS attack to occur on their website.
If it does, the users and the reputation of the brand will suffer. Your host won't be pleased to discover infected and compromised websites on their servers if you use a shared hosting service.
In most cases, your hosting company will simply take your website offline and keep it that way until you can fix the issue if hackers are able to carry out a cross-site scripting attack on it.
But a good host will go a little bit further than that.
Hosting companies that genuinely care about their clients' safety have real-time monitoring systems that can spot suspicious activity. This keeps the account owners informed and enables them to thwart the attack before it has a chance to harm too many users.
The amount of assistance your host can provide has some restrictions.
The provider can't fix security flaws in your website or develop your application for you. But if you pick the right host, you'll be able to rely on a group of support professionals who can point you in the right direction if you need more assistance.
How dangerous is cross-site scripting?
Because they frequently result in flexible attack vectors, XSS vulnerabilities are a favourite among hackers. Even though JavaScript is the most common programming language used in cross-site scripting attacks, many other coding scripts have flaws that can be taken advantage of. Even though Javascript only has a small amount of access to the victim's operating system, hackers can still use it to spread malware and successfully deface the website.
Meanwhile, XSS is a great account takeover tool due to the unrestricted access hackers have to user data and cookies.
What are the three primary XSS attack types?
There are three main categories of XSS attacks that can be distinguished based on how the malicious payload is executed.
We're talking about a stored (or persistent) XSS attack if the attacker is successful in embedding the payload within the vulnerable application.
What can XSS be used for?
You have a reflected cross-site scripting attack when the attacker uses a malicious URL to reflect the payload off the web application.
The attack qualifies as DOM-based if the malicious script is loaded directly into the browser's Document Object Model.
Conclusion
The effectiveness of the attack is demonstrated by the fact that more than 20 years later, the online community is still working to eradicate cross-site scripting. Nothing indicates a one-size-fits-all solution is on the horizon, so as a website owner, you must be aware of the threat and take all reasonable precautions to reduce the risk.
Fortunately, there is a wealth of knowledge available on how to run your application more securely. It's easier than ever to create stronger defences against XSS attacks.
FAQ
A cross-site scripting attack uses unfiltered user input to cause an unexpected response to be returned by a vulnerable web application. This makes it possible for attackers to run malicious scripts on the target's computer using the app.
