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fix(security): sanitize unescaped HTML interpolation in certificate download (#489) #524

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fix(security): sanitize unescaped HTML interpolation in certificate download (#489) #524

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34 changes: 28 additions & 6 deletions src/app/credentials/[credentialId]/page.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,20 @@ import {
import { useState, useCallback } from "react";
import { ShareButton } from "@/components/shared/share-button";

/**
* Safely escapes HTML special characters to prevent cross-site scripting (XSS)
* when interpolating dynamic data into raw certificate HTML templates.
*/
export function htmlEscape(value: unknown): string {
if (value === null || value === undefined) return "";
return String(value)
.replace(/&/g, "&")
.replace(/</g, "&lt;")
.replace(/>/g, "&gt;")
.replace(/"/g, "&quot;")
.replace(/'/g, "&#39;");
}

export default function CredentialDetailPage({
params,
}: {
Expand Down Expand Up @@ -67,8 +81,16 @@ export default function CredentialDetailPage({

const handleDownload = useCallback(() => {
if (!credential) return;
const escapedTitle = htmlEscape(credential.courseTitle);
const escapedIssued = htmlEscape(formatDate(credential.issuedAt));
const escapedId = htmlEscape(credential.id);
const escapedTokenId = htmlEscape(truncateAddress(credential.tokenId, 8));
const scoreHtml = credential.metadata?.score != null
? `<p class="meta">Score: ${htmlEscape(credential.metadata.score)}%</p>`
: "";

const html = `<!DOCTYPE html>
<html><head><title>Certificate - ${credential.courseTitle}</title>
<html><head><title>Certificate - ${escapedTitle}</title>
<style>
body{font-family:Georgia,serif;display:flex;justify-content:center;align-items:center;min-height:100vh;margin:0;background:#f9fafb}
.cert{background:white;border:2px solid #111;padding:48px;max-width:640px;text-align:center}
Expand All @@ -77,12 +99,12 @@ export default function CredentialDetailPage({
</style></head><body>
<div class="cert">
<h1>Certificate of Completion</h1>
<h2>${credential.courseTitle}</h2>
<h2>${escapedTitle}</h2>
<div class="line"></div>
<p class="meta">Issued: ${formatDate(credential.issuedAt)}</p>
<p class="meta">Credential ID: ${credential.id}</p>
<p class="meta">Token: ${truncateAddress(credential.tokenId, 8)}</p>
${credential.metadata.score ? `<p class="meta">Score: ${credential.metadata.score}%</p>` : ""}
<p class="meta">Issued: ${escapedIssued}</p>
<p class="meta">Credential ID: ${escapedId}</p>
<p class="meta">Token: ${escapedTokenId}</p>
${scoreHtml}
<div class="line"></div>
<p class="meta">Verified on Stellar blockchain</p>
</div>
Expand Down