This tutorial describes the types of XSS attacks and the best security measures to test your frontend code against such attacks. Moreover, it educates developers about programming best practices for secure coding.
What is Cross-Site Scripting (XSS)?
According to the statistics reported in , the ratio of XSS attacks as compared to other cybersecurity attacks per year is depicted below in the chart.
Types of XSS attacks
XSS attacks are generally categorized into three basic types.
- DOM-based XSS: When an attacker can read requested DOM elements by the victim and can send malicious scripts in response.
- Stored XSS: A database-based malicious script that plays with the incoming users' requests.
XSS Attacker Journey
An XSS attack is performed by the execution of malicious client-side code that is injected into a trusted web application by the attacker in the user-provided inputs by exploiting XSS vulnerabilities.
A graphical depiction of the XSS attacker journey is given below.
For instance, an attacker sends a trusted link with a malicious script embedded, as given below, to the victim to click on it. After clicking, the malicious script will be executed on the client’s system thus giving the client’s information to the attacker. The alert function depicted in the link below can be replaced with any malicious code. Similarly, the attacker can steal the sessions and cookies information of the victim and then masquerade as an actual user on the particular web application.
For a better understanding, let us consider a scenario where a web application takes input from the user and returns the search result against that input.
When this URL opens up at the client-side, it will look like this:
<p>Your search for 'flowers <script>MALICIOUS_SCRIPT ()</script>'
The function MALICIOUS_SCRIPT() will then be executed and may perform a very damaging effect on the client-side.
What are the Best Secure Code practices to avoid XSS Attacks?
The damages that occur due to the presence of XSS vulnerabilities could be catastrophic. Data or information leakage in the modern age is unbearable and could lead you to court. The greater the volume of user profiles on your web application, the higher will be the risk of cyberattacks and intrusions online. Therefore, your web application's cybersecurity and defense mechanism must be as important as its design and architecture.
Due to the high demand for web application security, software developers should always take care of the security breaches that might occur during the development process and after the production phase. The developers must adopt secure code practices to always stay on the safe side and perform efficiently. Some of the secure code practices include:
· Always go for development frameworks; they are mostly secure
· User-provided input fields must be handled securely
· Adopt encoding mechanism on the outputs
· Validate user inputs before processing
· Always follow the defense-in-depth principle
· Always follow cheat sheets provided by OWASP
· Use appropriate response headers
· Design content security policies
· Post-development analysis of the web application
· Stay updated on XSS preventions techniques and follow HacWare's secure code twitch series.
Due to the exponential growth of XSS attacks, many automatic XSS testing tools are now available online where you can test your web application at ease. A list of some free and paid XSS testing tools is given below.
- XSS Scanner
- OWASP zap XSS Scanner
- IBM Rational AppScan
- Burp Suite
- Zed Attack Proxy
- XSS Hunter
This tutorial highlights one of the most exploitable web application vulnerabilities. It also explains how attackers can compromise the web application functionalities and steal data from the client side. XSS vulnerabilities may result in a great loss and can bankrupt the company due to its user's data leakage. The mitigation of these vulnerabilities is very challenging as it requires extensive manual testing of the frontend code or by use of free/ commercial security tools available online. Similarly, XSS attacks can be avoided by following the attack prevention techniques and adopting secure code practices since the start of the project.
Check out our Cybersecurity API?
HacWare offers a powerful API for softwar developers to launch next generation (Next-Gen) cybersecurity education programs to combat phishing attacks with a few lines of code. To learn more about our powerful security awareness API and developer program, click here to apply .
HacWare makes it super easy for Software Developers and IT teams to launch hyper custom cybersecurity education solutions to combat phishing attacks. Learn more about HacWare at hacware.com.
Also, check out our free secure code streams on Twitch!