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Fix: XSS vulnerability with exception text (CodeQL #7) #29

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Fix: XSS vulnerability with exception text (CodeQL #7) #29

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06f559e
Fix: Prevent XSS vulnerability in error message display
jmaddington Mar 31, 2025
f655b5e
Fix: Prevent reflected XSS vulnerability in format error message
jmaddington Mar 31, 2025
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16 changes: 14 additions & 2 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,18 @@ function utf8ToAscii(str) {
.join('');
}

function escapeHtml(str) {
if (typeof str !== 'string') {
return '';
}
return str
.replace(/&/g, '&')
.replace(/</g, '&lt;')
.replace(/>/g, '&gt;')
.replace(/"/g, '&quot;')
.replace(/'/g, '&#39;');
}

function sanitizeErrorHeader(msg) {
if (typeof msg === 'string') {
return utf8ToAscii(msg).replace(/\r?\n|\r/g, '');
Expand Down Expand Up @@ -122,7 +134,7 @@ function failSvg(res, msg, statusCode = 500) {
</style>
<foreignObject width="240" height="80"
requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility">
<p xmlns="http://www.w3.org/1999/xhtml">${msg}</p>
<p xmlns="http://www.w3.org/1999/xhtml">${escapeHtml(msg)}</p>
</foreignObject>
</svg>`);
}
Expand Down Expand Up @@ -353,7 +365,7 @@ app.get('/chart', (req, res) => {
renderChartToPng(req, res, opts);
} else {
logger.error(`Request for unsupported format ${outputFormat}`);
res.status(500).end(`Unsupported format ${outputFormat}`);
res.status(500).end(`Unsupported format ${escapeHtml(outputFormat)}`);
}

telemetry.count('chartCount');
Expand Down