Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) can put many web apps at risk.
This article dives deep into the world of XSS and CSRF, giving you all the necessary information about these two important vulnerabilities.
It talks about the kinds you might encounter, how they’re used to attack, and how they can damage data security.
While they share similarities, these attacks are very different from each other, and if you’re starting out with cyber security, it’s easy to confuse them.
The purpose of this article, then, is to highlight the differences between them and explain clearly how they work.
Our journey ends with a side-by-side comparison table and how these attacks can be chained together. This gives a neat, full view of XSS vs CSRF's inner workings.
Ready? Let’s go.
Understanding XSS (Cross-Site Scripting)
XSS is a web security vulnerability where an attacker injects malicious scripts or queries—usually made in Javascript—into a vulnerable web application.
XSS is pretty common, as it’s the second most prevalent issue in the OWASP Top 10 and is found in around two-thirds of all applications. However, understanding its intricacies is surprisingly straightforward.
Overview of XSS Attacks
- Reflected XSS: In Reflected XSS, injected scripts are reflected off a web server to unsuspecting users, typically through a manipulated link, and executed in the user's browser. This exploit occurs in real-time, leveraging the web application's immediate processing of user input.
- Stored XSS: In Stored XSS, the malicious injected scripts are permanently stored on the target website. This way, when attackers inject these scripts, they do it directly into the site's database, and when users access the compromised page, the stored script executes in their browsers, potentially leading to the unauthorized access and manipulation of sensitive user data.
- DOM-Based XSS: In DOM-Based XSS, attackers manipulate a webpage's Document Object Model (DOM) through the injected malicious scripts. These scripts dynamically alter the page's structure. When users interact with the modified content, the injected script executes in their browsers, opening the door to compromising sensitive information and enabling actions otherwise not allowed by the user.
XSS Example
XSS attacks take advantage of web application vulnerabilities—for example, a webpage that includes user input from the URL without proper sanitization.
Think about how your search term appears in the URL when Googling something.
This circumstance is harmless, but imagine if a username is included. What about a product’s price? Or a session cookie? What could potentially result from changing this information?
And what about inserting a PHP or Javascript command? If the website doesn’t sanitize this type of input, the code could be executed on the page.
An attacker might create a harmless-looking link but hide malicious code within it. Unknowingly, when a user clicks this link, the hidden malicious code springs into action.
For example, if a session cookie is included in the URL, and the site doesn’t sanitize scripts inserted in the URL, an attacker could write a script that sends the session cookie to an attacker-controlled server.
Now they just need a victim to click on it.
The more dangerous scenario is that some type of input on the site, such as a comment box, can take a similar script and store it. Now it executes every time the page is visited, sending session cookies to the attacker.
Here, trust is manipulated since users may not realize the lurking danger. This draws attention to the need for strong security steps.
The key takeaway is that in this scenario, the website is being tricked into executing malicious code.
Impact of XSS Attacks
When attackers find XSS vulnerabilities, they can potentially get their hands on private user information. This can mean someone's account gets taken over, data is manipulated, or personal details are stolen.
Also, XSS can lead the attackers to change the website, inject malicious content, or redirect users to harmful sites.
Understanding CSRF (Cross-Site Request Forgery)
Cross-Site Request Forgery (CSRF) is a cyber security vulnerability where attackers trick users into executing unwanted actions on a website where they are authenticated.
Unlike XSS, which exploits trust between users and websites, CSRF manipulates a website's trust in a user's browser.
Overview of CSRF Attacks
CSRF attacks often use malicious URLs or forms crafted by the attacker.
When a logged-in (authenticated) user triggers these, they can cause serious unwanted actions on the target site, from deleting accounts to making unauthorized actions and even full account breaches.
CSRF Example
At a high level, CSRF capitalizes on how web browsers naturally include saved session cookies in requests to certain domains.
This lets attackers create harmful requests, which users are tricked into running unknowingly. Trusting in the authenticity of the session, the browser sends these requests.
This results in unexpected actions on the target vulnerable website, causing the damage we already talked about.
Let’s see how it works in a hypothetical situation:
- Based on a vulnerable website, the attacker forges a request for a fund transfer from the victim’s bank account to their own bank account.
- The attacker creates a form that looks innocent and puts it on a malicious website.
- The attacker then sends the link to the malicious website to their victim, who clicks on it and opens it in their browser while being authenticated to their bank account.
- This triggers the malicious request, which is validated and accepted by the vulnerable bank website as legitimate.
- Last, the attacker receives the money the victim inadvertently sent him without noticing.
The example is illustrated below
CSRF attacks leverage HTTP requests (the language browsers use to communicate with websites) and cookies (small data packets storing session information).
By manipulating these, attackers essentially hijack the user's session, temporarily gaining control of their account.
The takeaway is that because the website doesn’t have any mechanism to ensure the requests are legitimate, it simply processes the request. The user is being tricked into requesting the action.
Impact of CSRF Attacks
User accounts and data integrity can be directly affected by CSRF attacks. It also puts at risk the full safety of web applications since very often, attackers use CSRF to launch bigger attacks.
They utilize the exposed user session to gain more power, access private features, or carry out even more attacks that can affect the app's security.
What Are the Key Differences Between XSS vs CSRF?
XSS and CSRF might seem alike initially. But, they're distinct under scrutiny. In the next section, we're untangling the differences between these two vulnerabilities and highlighting their individual traits.
What Do XSS and CSRF Attacks Have in Common?
- Web App Vulnerabilities: Both XSS and CSRF exploit vulnerabilities within web applications, taking advantage of weaknesses that may exist in how user input is handled or how session management is developed.
- Compromise User Data Security: XSS and CSRF share the potential to compromise user data security through different mechanisms. Understanding the nature of these mechanisms is important for developing effective defense strategies.
- Preventative Measures: Despite their differences, XSS and CSRF need proactive defense measures. Implementing robust secure methods, such as input validation and secure session management, is fundamental to prevent potential attacks and safeguard user data.
What Are the Key Differences Between XSS and CSRF Attacks?
- The Nature of the Attacks:
- In XSS, the attacker uses the user's trust in a website to their advantage. They sneak harmful scripts into the web page, usually by finding gaps in how user input is dealt with.
- In contrast, CSRF abuses a website's trust relationship with a user's browser. The attacker fools the browser into doing things on a site that the user didn't intend to do.
- Attack Vectors:
- XSS is usually about injecting harmful scripts into web pages users view. Once there, these scripts can run in the user's browser and may endanger private data.
- CSRF tricks users into doing actions they didn't approve of on a website they’re logged into. CSRF takes advantage of browsers automatically putting authentication cookies in their requests, causing users to kick off actions without knowing they did.
- User Interaction:
- For XSS, harmful scripts can run on their own when users visit a corrupted page, and no human action is needed.
- In CSRF attacks, users need to do someth ing, like click a phishing link or load up a malicious page.
How to Prevent XSS and CSRF
Now, let's see the most effective ways to prevent XSS and CSRF and secure web applications.
The Deadly Duo (Combined Attacks)
We use the term "Deadly Duo" to describe a serious online threat.
This is when the attacker combines Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF).
This partnership makes it easier for them to break into web applications. To stop them, we need to understand how XSS and CSRF work together to make this “duo” more harmful.
In a classic Deadly Duo case, an attacker starts with an XSS attack, and they trick a website into running harmful scripts.
When people visit the affected web pages, the script can control the victim’s browsers and make unauthorized actions on the hacked user’s behalf.
The attacker uses it to set up and execute a CSRF attack, and no action is required by the user beyond visiting the website.
This could mean that the attackers will be able to move money, change account details, or any action the user could take. The user doesn't know this is happening.
XSS vs CSRF vs SSRF
SSRF stands for Server Side Request Forgery. It is another common web application vulnerability that involves manipulating requests.
We’ve examined XSS and CSRF in detail. In short, XSS sneaks a command into the application that tricks a browser into performing an unwanted action. CSRF, on the other hand, manipulates the browser into making an unwanted request of the web application.
SSRF tricks the web application into grabbing information it shouldn’t.
A simple example of SSRF would be a website that lets you download images, audio files, or some other media by providing a URL. All the web application knows is it should go to the desired URL and pull the requested content.
Now, instead of a URL to an image or document, you give it the URL of it’s own admin panel. It might look like http://localhost/admin.
A vulnerable application wouldn’t check what the URL is or filter these types of requests - instead it tries to return access to you. This type of attack doesn’t require a third victim, it takes place entirely between the attacker and the application.
Exploiting this vulnerability, an attacker could potentially gain access to sensitive information within a database (such as personal information of users or back-end data) or access to system controls if they are not properly safeguarded.
Conclusion
In conclusion, we've looked deep into the similarities between XSS’ and CSRF, highlighting their differences and explaining how they work and how they can affect you and your web application.
XSS works by breaking down user trust, while CSRF manipulates the bonds between site and browser.
If you want to learn how to test for these vulnerabilities and defend against them, try a StationX membership.
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