The growth of cyber awareness and the impact of cyberattacks is what has led to us knowing how to differentiate “Nigerian prince email scams” from genuine emails. However, we are still nowhere close to where we should be with hackers ever-evolving, and us constantly falling victim to cyberattacks, especially when it comes to the attack tactics of cross-site scripting, otherwise known as ‘XSS.’ PayPal, Facebook, and Google have been its victims, and it is so widespread that it has made its way to OWASP’s most critical web application security report since 2003. 
What is Cross-site Scripting (XSS)?
Cross-site scripting is a type of injection security attack where an attacker intrudes the communication and injects data to make the script of otherwise trusted websites malicious. XSS attacks occur when an untrusted source gains access to insert malicious code in a trusted web application, which is then delivered to a victim’s browser. The longer the attacker has access, the more threats are spread. Hence, it calls for a deeper understanding of attacks as well as security measures and identification of suspicious behavior on the network.
Cross-site scripting allows attackers to hide malicious code without it being noticed by website developers. The decryption capabilities of the encrypted data are crucial when identifying a XSS attack.
|Example of XSS:
Suppose a website has a messaging feature where users can send messages to their contacts.
A basic script for this function will be as follows:
<form action=”sendmessage.php” method=”post'”>
<textarea name=”message”> </textarea>
<input type=”submit” value=”send” />
This form, when submitted stores the message in the database, which is then sent to the recipient’s inbox. When an attacker sends a cookie-stealing script in the message, the malicious script is stored on the website. When another person tries to read it, the cookie-stealing script executes the attack and the session ID of the person accessing the message is transferred to the attacker. As soon as the attacker receives access to valid session ID, he can hijack others’ accounts.
How do attackers use XSS?
Cross-site scripting is of three forms – reflected, stored, and document object model. The malicious user can use the script in all these forms. Their elaborated description is as follows:
Reflected Cross-site Scripting (XSS)
If you ever happen to come across a shortened link or receive a content pop up on your social media feed, then beware, you may be the next victim of an XSS attack.
Stored (Persistent) Cross-site Scripting (XSS)
Document Object Model (DOM) Cross-site Scripting (XSS)
A document object model (DOM) is an API that represents the page and defines the logical stricture of XML and HTML documents. It allows the attacker to change the document content, style, and structure. DOM-based attacks occur when a web application writes data to the DOM. The attacker modifies the DOM environment with a malicious payload, and when the script is executed, the client-side code runs that payload. Unlike the other two models, DOM-based attacks involve in-depth analysis of code flow, and hence, they are challenging to troubleshoot.
Preventing Cross-Site Scripting
There are many ways to prevent cross-site script attacks, but we will focus broadly on the three most effective preventive techniques:
1. Validate user input
Validating user input tests all user application inputs and blocks inaccurate information from entering the system. It restricts the users from inserting special characters into dropdown form fields.
2. Sanitize user input
This preventive method is helpful for websites that allow HTML markup with data scrub to eliminate harmful or unacceptable user input. Sanitizing user input such as ‘GET’ or ‘POST’ parameters and cookies will help you prevent XSS attacks.
3. Content security policy
It is a policy that defines rules to access content from safe sources and thus restricts malicious content. A content security system will have instructions laid down on accessing content from a specific domain.
Beyond Preventive Measures
A security analyst must proactively handle the security of all the systems and must be able to detect malicious code. They must ensure that the security team can detect the difference between legitimate and illegitimate traffic. This requires close collaboration in the group to identify the attack surface and a monitoring tool that can analyze encrypted traffic.
It is also the responsibility of web developers to prevent XSS attacks by following a secure development life cycle, scan them for vulnerabilities, and protect them with a firewall. After all, its business reputation that matters.
Advanced attacks like cross-site scripting require cybersecurity expertise to be identified and prevented. A bachelor and master program in cybersecurity will help gaining the required knowledge of various attack vectors, tools, and methodologies to combat them.
EC-Council University is dedicated to creating excellent educational programs in the stream of cybersecurity. The programs will equip graduates with the knowledge to assess the latest IT security risks and expert skills to handle them successfully. The university offers Bachelor and Master programs at the degree level. The Bachelor of Science in Cybersecurity (BSCS) gives required exposure, builds cybersecurity skills, and develops leadership abilities that help any candidate to grow as a cybersecurity professional. Master of Science in Cybersecurity (MSCS) makes you an expert in desired skills and helps you in gaining domain knowledge to stand ahead in the competition.
ECCU is accredited by Distance Education Accrediting Commission (DEAC) which is a recognized accrediting agency by the U.S. Department of Education and is also an acknowledged member of the Council for Higher Education Accreditation (CHEA).
ECCU has industry practitioners as faculty members who also serve as mentors for the students when they aspire to get into cybersecurity. The iLabs facility from the university helps in gaining hands-on practice to the students.