Cross-Site Scripting in UI Components

DOM-based XSS vulnerabilities in JavaScript UI libraries pose significant risks to modern web applications. Popular frameworks and component libraries have suffered XSS vulnerabilities that affect all applications using them. These vulnerabilities often involve improper sanitization of user input before DOM manipulation or unsafe use of innerHTML. The React framework's dangerouslySetInnerHTML API explicitly acknowledges this risk, but vulnerabilities still emerge when libraries handle user input incorrectly.

Template injection vulnerabilities in server-side rendering libraries allow attackers to execute arbitrary code within template contexts. These vulnerabilities blur the line between XSS and RCE, potentially allowing server-side code execution through client-side vectors. Template engines like Handlebars, Pug, and others have experienced such vulnerabilities, often arising from insufficient separation between template code and user data.

CSS injection vulnerabilities in styling libraries might seem less severe but can enable sophisticated attacks including data exfiltration and clickjacking. Libraries that dynamically generate CSS based on user input without proper sanitization create opportunities for attackers to inject arbitrary styles. These attacks can steal data through CSS-based timing attacks or manipulate page layout to trick users into unintended actions.