Cross-Site Scripting (XSS) Types: The 3 Most Dangerous Forms

By Tibor Moes / Updated: June 2023

Cross-Site Scripting (XSS) Types: The 3 Most Dangerous Forms

Cross-Site Scripting (XSS) Types

Picture a crowded marketplace bustling with activity. There’s a fruit seller selling what seems to be delicious apples. Little do you know, some of these apples are rotten inside. This is quite like the digital world, where the friendly-looking website you’re visiting could be tainted by Cross-Site Scripting (XSS). Stick around, and let’s peel back the layers of this digital hazard.


Cross-Site Scripting, or XSS, is a digital trick that allows hackers to plant malicious scripts into web pages viewed by other users. These scripts can steal data, alter web content, and perform other harmful activities, creating a dangerous and deceptive digital environment.

Type 1 – Stored XSS (Persistent): This is like a time bomb, where the malicious script is permanently stored on the target servers. It gets triggered every time a user accesses the tainted webpage, making it a constant threat.

Type 2 – Reflected XSS (Non-Persistent): More of a sniper’s shot, the malicious script is embedded in a URL. It only affects users who click on the manipulated link, turning innocent clickers into potential victims.

Type 3 -DOM-based XSS: This is like a hidden trap, exploiting the structure of web pages. The malicious script manipulates the Document Object Model (DOM) of a webpage, creating traps that can be triggered even after the page has loaded.

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Cross-Site Scripting (XSS) Types In-depth

Stored XSS (Persistent)

You know how in spy movies there’s always that suspenseful scene where a time bomb is hidden somewhere, and it’s just waiting to explode at the right moment? Well, that’s similar to what happens in a Stored XSS attack, also known as Persistent XSS.

Let’s say you’re visiting your favorite online forum, maybe it’s about gardening, tech gadgets, or even the best types of pizza toppings. You’re there to have a chat, to learn something new, and to share your thoughts. Harmless, right? But unbeknownst to you, someone, let’s call them Mr. X, has left a little ‘gift’ in one of the forum posts.

This ‘gift’ is not the kind you’d like to receive though. It’s a nasty piece of computer code, or script, hidden within an innocent-looking post. It’s a wolf in sheep’s clothing. And the worst part? It’s there to stay, permanently stored on the server, hence the term ‘Stored XSS’.

Every time you, or anyone else, accesses that tainted forum post, the nasty script springs to life. It can cause all sorts of mischief like stealing your personal information, taking over your account, or even turning your computer into a puppet for Mr. X to control. Just think of it as a digital puppeteer pulling your strings without you even realizing it.

It’s like eating a piece of candy, only to find out too late that it was laced with something harmful. The candy, in this case, is the innocent-looking forum post, and the harmful substance is the hidden script.

What makes Stored XSS particularly dangerous is its persistent nature. Once the malicious script is planted, it doesn’t just go away. It stays there, lurking, ready to cause harm over and over again. It’s not a one-time event but a continuous threat, making it a serious concern for website security.

To counter this, we need to have diligent digital hygiene. Websites need to carefully sanitize, or clean up, their input data. Just like washing hands before a meal, websites need to ensure that any content they accept from users doesn’t contain any hidden surprises.

And that’s a glimpse into the world of Stored XSS, the digital time bomb. Remember, the online world might seem benign, but we need to be vigilant. As the saying goes, not everything that glitters is gold! So, let’s keep our eyes open, stay informed, and make the digital space a safer place for all of us.

Reflected XSS (Non-Persistent)

Imagine walking through a bustling city. Street vendors are selling their wares, music is playing, and people are laughing. Suddenly, a mischievous prankster from a balcony drops a water balloon on you. It came out of nowhere, and only you got soaked. That, in essence, is a Reflected XSS attack, also known as Non-Persistent XSS.

In our digital city, the streets are websites, the vendors are the clickable links, and the prankster? Well, that’s a hacker armed not with a water balloon, but with a malicious piece of code or script. And that unsuspecting pedestrian who got drenched? That’s an innocent user clicking on a tainted link.

Reflected XSS is a bit like digital fast food. It’s quickly delivered, consumed instantly, and then it’s gone. The mischief-maker, Mr. X, cleverly hides the malicious script within a URL. This could be in an email, a social media post, or any digital place where you can click on a link. It looks as ordinary as any other URL. But here’s the trick: when you click on it, the malicious script is reflected off the server, like a sniper’s bullet ricocheting off a wall, and fires back at you.

Once the script has sprung into action, it can do a lot of damage. It can steal your data, infect your computer, or take control of your account. It’s a sniper’s shot: targeted, precise, and damaging.

But unlike Stored XSS, the Reflected XSS is not a persistent threat. It’s a one-time event, like the water balloon prank. Once you click the link and the script is activated, it’s done. If you don’t click the link, the threat never materializes.

So how do we dodge this digital water balloon? Well, it’s all about being cautious about what we click on. Think of it as checking both sides of the street before crossing. If a link looks suspicious, or it’s from a source you don’t trust, it’s best not to click on it. Remember, curiosity killed the cat!

On the other side of things, websites also need to sanitize their input data and encode their output data. This makes sure that if there’s any mischievous code hiding in a URL, it gets cleaned up before it can cause any trouble.

And that’s our journey through the digital city with Reflected XSS, the sniper shot of the digital world. As we stroll through the city, let’s stay alert, stay safe, and keep enjoying the sights and sounds of the digital world.

DOM-based XSS

Think about an exciting adventure movie where our hero enters an ancient temple filled with treasure. It all seems quiet and harmless, right? But then, out of nowhere, a trap door opens, or a stone wall starts to move. Unseen mechanisms were waiting for just the right moment to spring their traps. This is quite like a DOM-based XSS attack.

The treasure temple in our digital adventure is a website, and the mechanisms are the website’s structure, or what we call the Document Object Model (DOM). The DOM is like the skeleton of a website. It defines how the website is structured, how different elements interact with each other, and how the website changes and updates.

Now, our digital trickster, Mr. X, likes to play with these mechanisms. He crafts a cunning piece of code, a script, that doesn’t attack the website directly. No, that would be too obvious. Instead, the script targets the website’s structure, the DOM. By manipulating the DOM, the script can change what the website displays or does. It’s like the hidden lever in the temple that activates the trap door.

This is why we call it DOM-based XSS. It’s an XSS attack that plays with the DOM to achieve its mischievous goals. The script can be hidden in a URL, just like in a Reflected XSS attack. But here’s the twist: the malicious script never really talks to the server. It’s all happening on the client side, within your own browser. It’s a local problem, not a server problem.

The traps can be dangerous. They can steal sensitive information, manipulate web content, or perform actions on your behalf. It’s as if our adventure hero, instead of finding treasure, finds himself in a snake pit.

But don’t worry, there are ways to outsmart these traps. Just like our hero would use a map to navigate the temple, we can use caution when interacting with websites. Avoid clicking on suspicious links and always check the URL before proceeding.

For the web developers out there, a crucial countermeasure is to properly manage the website’s DOM. Think of it as maintaining the mechanisms of the temple. By using secure coding practices, developers can ensure that any potential traps are deactivated before they can harm anyone.

And there you have it, the hidden traps of the DOM-based XSS. But don’t let these traps scare you away from the digital temple. With knowledge and caution, we can safely navigate this intricate world. So, let’s continue the adventure, and keep discovering the treasures of the digital realm.


Navigating the world of Cross-Site Scripting is a bit like exploring a digital jungle. It’s filled with exciting opportunities, but also concealed hazards. We’ve journeyed through the Persistent, or Stored XSS, the ticking time bomb, the Reflected XSS, the sniper shot, and the DOM-based XSS, the hidden trap. These are different tactics that cyber tricksters use to create mischief. But with understanding, caution, and safe browsing habits, we can turn this jungle into a well-tread park. So keep exploring, stay curious, and remember to always stay safe in the digital world.

How to stay safe online:

  • Practice Strong Password Hygiene: Use a unique and complex password for each account. A password manager can help generate and store them. In addition, enable two-factor authentication (2FA) whenever available.
  • Invest in Your Safety: Buying the best antivirus for Windows 11 is key for your online security. A high-quality antivirus like Norton, McAfee, or Bitdefender will safeguard your PC from various online threats, including malware, ransomware, and spyware.
  • Be Wary of Phishing Attempts: Be cautious when receiving suspicious communications that ask for personal information. Legitimate businesses will never ask for sensitive details via email or text. Before clicking on any links, ensure the sender's authenticity.
  • Stay Informed. We cover a wide range of cybersecurity topics on our blog. And there are several credible sources offering threat reports and recommendations, such as NIST, CISA, FBI, ENISA, Symantec, Verizon, Cisco, Crowdstrike, and many more.

Happy surfing!

Frequently Asked Questions

Below are the most frequently asked questions.

Is XSS only a threat to outdated or poorly built websites?

No, even the most modern and well-built websites can fall victim to XSS attacks. It depends on the security measures they have in place, not the sophistication or newness of the website.

Can my personal computer be directly attacked with XSS?

Not exactly. XSS attacks typically target websites and the data within them. However, if you’re using a website that’s been attacked, your personal data or activities on that website could be compromised.

How can I protect myself from XSS attacks?

Always be cautious about the links you click on, and only provide personal information on secure websites that you trust. Keep your browser updated as most browsers have built-in protections against such attacks. You can also use security-focused browser extensions for an additional layer of protection.

Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor is a Dutch engineer and entrepreneur. He has tested security software since 2014.

Over the years, he has tested most of the best antivirus software for Windows, Mac, Android, and iOS, as well as many VPN providers.

He uses Norton to protect his devices, CyberGhost for his privacy, and Dashlane for his passwords.

This website is hosted on a Digital Ocean server via Cloudways and is built with DIVI on WordPress.

You can find him on LinkedIn or contact him here.

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