Sanitize comment rendering in xxe.js

[hcl-appscan-rapidfix]

Pixee Scan: 1d7ceb7a-349b-4361-a889-1ac1bb34bc8e

Confidence: HIGH

Fix confidence is a rating derived from an internal benchmark and includes High, Medium, and Low confidence fixes. It comprises three weighted scores reflecting the safety, effectiveness and cleanliness of Pixee's code changes within a fix. View Details in Pixee.

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Remediation

This change fixes finding d3af0015-9e3c-f111-8ef3-00224854fbc5.

Details

Sanitize comment rendering in xxe.js

Summary

Sanitize comment rendering in xxe.js.

Vulnerability Description

Cross-Site Scripting occurs when untrusted data is inserted into a web page without proper escaping or sanitization. An attacker can inject script or markup that executes in a victim’s browser, which can expose session data, alter page behavior, or perform actions on the user’s behalf. This is especially dangerous when the application renders data that originated from other users or from server responses.

Changes Made

The comment renderer in src/main/resources/lessons/xxe/js/xxe.js built HTML by directly substituting server-returned fields into a template and appending the result to the page. That pattern was dangerous because result[i].user, result[i].dateTime, and result[i].text could reach a DOM XSS sink without escaping. The fix added an escapeHtml helper that encodes the standard HTML metacharacters, and the renderer now passes each of those fields through that helper before inserting them into the template. This preserved the existing UI structure while making the comment output safe to render.

Guidance Adherence

Source: Pixee Knowledge Base

Applied the following guidance from the remediation instructions:

• Sanitize untrusted user input before rendering it in HTML responses: the fix adds escapeHtml() and uses it on result[i].user, result[i].dateTime, and result[i].text before interpolating them into the html template, which prevents script/markup injection when the comment list is appended to the DOM.
• Use framework-appropriate escaping functions or sanitization libraries: this codebase is plain JavaScript/jQuery, so a small local escaping helper is an appropriate framework-neutral escaping approach; it escapes &, <, >, ", and ', covering the common HTML-breaking characters needed for this sink.
• Preserve the existing rendering flow while neutralizing taint at the sink: the patch keeps the $.get(...)->replace(...)->append(...) flow intact and applies encoding right before the HTML sink, which matches the guidance’s focus on safe output encoding rather than changing application behavior.

No new external library was introduced, so no dependency manifest update was necessary.