Advanced Techniques for Bypassing Web Filters: A Practical Guide to Identifying and Exploiting XSS Vulnerabilities

In web application security, Cross-Site Scripting (XSS) vulnerabilities are a common yet powerful threat, enabling attackers to execute scripts in a user’s browser. Security-conscious developers often employ various filters to prevent XSS, but crafty attackers can bypass these filters with the right techniques. This guide provides a technical breakdown of filter evasion tactics, showcasing real-world solutions to bypass common XSS filters and restrictions.

Below you can find a collection of bypasses which can be tried over at https://labs.hackxpert.com/RXSS/GET/

1. Identifying Filter-Free Fields

The first step to a successful XSS exploit is to identify fields with little or no filtering. For instance, in lab 01 where “no filters at all” are present, any XSS payload can be injected, making it trivial to execute malicious code. However, as filtering layers are added, attackers must adapt.

2. Bypassing Basic Script and Event Filters

In many scenarios, applications filter out the <script> tag and certain JavaScript functions like alert() to prevent basic XSS (Lab 10). Common evasion methods include using…