Top Tips To Battling Cross-Site Scripting

Cross-Site Scripting

Also known as XSS, cross-site scripting attacks come in two major forms – reflected and stored (sometimes referred to as persistent). Reflected XSS is the process of reflecting malicious script into a page link. Stored XSS is the process of injecting malicious script directly into the vulnerable application. XSS vulnerabilities are common and have affected applications such as PayPal, Google, and even Facebook. So, how can you kick cross-site scripting out of your applications and protect yourself from cyber threats? Let’s find out more!

Sanitizing User Input

While user input sanitation itself is a strong defense measure, you should not use it alone to combat XSS attacks. This method is extremely helpful on sites that enable HTML markup. Sanitizing data ensure that they do not harm users and your database. It scrubs any incoming data clean of potentially harmful markup and changes unacceptable user input to an acceptable format.

Input Validation

It is recommended that you treat any untrusted data as malicious entities. So, what’s untrusted data? It is anything that originated from outside your networking system. Oftentimes, you do not have absolute control over the data, e.g. request headers, cookies, query strings, web services, etc. When you aren’t 100% confident that the data set doesn’t contain evil stuff – treat them as untrusted.

Next, input validation is the process of ensuring an application is preventing malicious data from doing harm to one’s users, database, and site. In addition, it helps render the correct data. Input validation can also prevent a user from adding special characters into the fields. Yes, they do not refuse the request. Now, the Open Web Application Security Project (OWASP) has stated that input validation is not a primary XSS prevention method. It is designed to mitigate risks when a cybercriminal discovers a vulnerability.

Escape User Input

Escaping user input is often used as the first step of preventing cross-site scripting vulnerabilities from appearing in one’s applications. This method involves taking the data an application has received, checking whether it is secure or not, and then rendering it for the end user when the coast is clear.

When you escape user input, certain key characters in the data will be prevented from being interpreted in a malicious manner. In other words, you are censoring the data your web page receives in a way, in which characters such as < and > characters, are being disallowed. So, if you want your web page to disallow users from adding their own code to the page, consider escaping JavaScript, URL, and HTML entities.

They May Not Be 100% Foolproof!

The XSS prevention methods above are stellar ways to prevent the majority of such attacks. However, you should keep in mind that they only cover MOST of the cross-site scripting attack vectors. They will not cover everything. If you want to be truly vigilant against XSS and other potentially debilitating vulnerabilities, you should utilize a mix of code review, dynamic testing when the application goes live, proactive monitoring, and automated static testing during development stages. All in all, you should always make it a point to ensure secure coding practices from the get-go.