Kotlin XSS Guide: Examples and Prevention

A Kotlin web application is susceptible to cross-site scripting (XSS) attacks, a common security vulnerability that allows attackers to inject malicious JavaScript code into web pages. This vulnerability often arises in web applications that accept user input, such as online forums or search queries. Two primary examples illustrate how XSS attacks can exploit these weak points: first, by manipulating URL query strings to inject scripts, and second, by embedding malicious JavaScript in persistent user-generated content like comments, which are stored in databases. Prevention strategies include sanitizing and validating user inputs before processing or storing them, utilizing a template engine like FreeMarker for rendering HTML, and configuring Ktor’s respondText() method to render content as plain text to mitigate risks. These measures are essential to safeguard applications and users from XSS attacks.