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fix: escape fallback raw-content ancestor tags in templates and processing instructions #39

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Merged
alan-agius4 merged 1 commit into from
Aug 20, 2026
Merged

fix: escape fallback raw-content ancestor tags in templates and processing instructions #39

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22 changes: 17 additions & 5 deletions lib/NodeUtils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -135,11 +135,17 @@ function attrname(a) {

function fallbackRawContentTags(node) {
const tags = [];
while (node?.nodeType === 1 /*ELEMENT_NODE*/) {
if (node.namespaceURI === NAMESPACE.HTML && hasRawContentFallback[node.tagName]) {
tags.push(node.localName);
while (node) {
if (node.nodeType === 1 /*ELEMENT_NODE*/) {
if (node.namespaceURI === NAMESPACE.HTML && hasRawContentFallback[node.tagName]) {
tags.push(node.localName);
}
node = node.parentNode;
} else if (node.nodeType === 11 /*DOCUMENT_FRAGMENT_NODE*/ && node._host) {
node = node._host;
} else {
node = node.parentNode;
}
node = node.parentNode;
}
return tags;
}
Expand Down Expand Up @@ -309,7 +315,13 @@ function serializeOne(kid, parent) {
s += '<!--' + commentData + '-->';
break;
case 7: //PROCESSING_INSTRUCTION_NODE
const content = escapeProcessingInstructionContent(kid.data);
let content = escapeProcessingInstructionContent(kid.data);
if (content.includes('</')) {
const fallbackTags = fallbackRawContentTags(parent);
for (const fallbackTag of fallbackTags) {
content = escapeMatchingClosingTag(content, fallbackTag);
}
}
s += '<?' + kid.target + ' ' + content + '?>';
break;
case 10: //DOCUMENT_TYPE_NODE
Expand Down
13 changes: 12 additions & 1 deletion lib/htmlelts.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1141,10 +1141,21 @@ define({
ctor: function HTMLTemplateElement(doc, localName, prefix) {
HTMLElement.call(this, doc, localName, prefix);
this._contentFragment = doc._templateDoc.createDocumentFragment();
this._contentFragment._host = this;
},
props: {
content: { get: function() { return this._contentFragment; } },
serialize: { value: function() { return this.content.serialize(); } }
serialize: { value: function() { return this.content.serialize(); } },
cloneNode: {
value: function(deep) {
var clone = HTMLElement.prototype.cloneNode.call(this, deep);
if (deep) {
clone._contentFragment = this._contentFragment.cloneNode(true);
clone._contentFragment._host = clone;
}
return clone;
}
}
}
});

Expand Down
69 changes: 69 additions & 0 deletions test/domino.js
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Expand Up @@ -1556,3 +1556,72 @@ exports.worksWithBase64DataImages = function () {
'iVBORw0KGgoAAAANSUhEUgAAAAgAAAAIAQMAAAD+wSzIAAAABlBMVEX///+/v7+jQ3Y5AAAADklEQVQI12P4AIX8EAgALgAD/aNpbtEAAAAASUVORK5CYII);"></div>'
);
};

exports.processingInstructionClosingTagEscapedInNoscript = function () {
const document = domino.createDocument('<html><body></body></html>');
const noscript = document.createElement('noscript');
noscript.appendChild(document.createProcessingInstruction('x', '</noscript '));
const img = document.createElement('img');
img.setAttribute('src', 'x');
img.setAttribute('onerror', 'alert(1)');
noscript.appendChild(img);
document.body.appendChild(noscript);

const html = document.body.serialize();
html.should.equal(
'<noscript><?x &lt;/noscript ?><img src="x" onerror="alert(1)"></noscript>'
);
html.should.not.containEql('<?x </noscript');
};

exports.processingInstructionClosingTagEscapedForAllFallbackElements = function () {
const document = domino.createDocument('');
for (const tagName of ['noscript', 'iframe', 'noembed', 'noframes']) {
const fallback = document.createElement(tagName);
fallback.appendChild(document.createProcessingInstruction('x', '</' + tagName + '/'));
document.body.appendChild(fallback);

const html = document.body.serialize();
html.should.containEql('<?x &lt;/' + tagName + '/?>');
html.should.not.containEql('<?x </' + tagName);
document.body.removeChild(fallback);
}
};

exports.templateContentInFallbackElementsEscaped = function () {
const document = domino.createDocument('');
for (const tagName of ['noscript', 'iframe', 'noembed', 'noframes']) {
const fallback = document.createElement(tagName);
const template = document.createElement('template');
const xmp = document.createElement('xmp');
xmp.textContent = '</' + tagName + '><img src=x onerror=alert(1)>';
template.content.appendChild(xmp);
fallback.appendChild(template);
document.body.appendChild(fallback);

const html = document.body.serialize();
html.should.equal(
'<' + tagName + '><template><xmp>&lt;/' + tagName + '><img src=x onerror=alert(1)></xmp></template></' + tagName + '>'
);
document.body.removeChild(fallback);
}
};

exports.clonedTemplateContentMaintainsHostReference = function () {
const document = domino.createDocument('');
const fallback = document.createElement('noscript');
const template = document.createElement('template');
const xmp = document.createElement('xmp');
xmp.textContent = '</noscript><img src=x onerror=alert(1)>';
template.content.appendChild(xmp);

const clonedTemplate = template.cloneNode(true);
fallback.appendChild(clonedTemplate);
document.body.appendChild(fallback);

const html = document.body.serialize();
html.should.equal(
'<noscript><template><xmp>&lt;/noscript><img src=x onerror=alert(1)></xmp></template></noscript>'
);
};

118 changes: 118 additions & 0 deletions test/xss.js
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Original file line number Diff line number Diff line change
Expand Up @@ -869,3 +869,121 @@ exports.fallbackRawTextForeignContentEscapesAncestorClosingTag = async function
}
}
};

exports.fallbackRawTextTemplateContentEscapesAncestorClosingTag = async function () {
const fallbackTags = ['noscript', 'iframe', 'noembed', 'noframes'];

for (const tag of fallbackTags) {
// noscript/iframe/noembed/noframes > template > xmp
{
const document = domino.createDocument('');
const fallbackEl = document.createElement(tag);
const template = document.createElement('template');
const xmp = document.createElement('xmp');
xmp.textContent = `</${tag}><img src=x onerror=alert(1)>`;
template.content.appendChild(xmp);
fallbackEl.appendChild(template);
document.body.appendChild(fallbackEl);

const serialized = document.body.serialize();
serialized.should.equal(
`<${tag}><template><xmp>&lt;/${tag}><img src=x onerror=alert(1)></xmp></template></${tag}>`,
);

const reparsedDoc = domino.createDocument('<body>' + serialized + '</body>');
reparsedDoc.getElementsByTagName('img').length.should.equal(0);

const reparsed = reparsedDoc.body.innerHTML;
reparsed.should.not.containEql(`</${tag}><img`);
const alerted = await alertFired(reparsed);
alerted.should.equal(
false,
`alert fired after normal HTML reparse for template xmp in <${tag}>: ` + reparsed,
);
}

// noscript/iframe/noembed/noframes > template > #comment
{
const document = domino.createDocument('');
const fallbackEl = document.createElement(tag);
const template = document.createElement('template');
const comment = document.createComment(`</${tag}><img src=x onerror=alert(1)>`);
template.content.appendChild(comment);
fallbackEl.appendChild(template);
document.body.appendChild(fallbackEl);

const serialized = document.body.serialize();
serialized.should.equal(
`<${tag}><template><!--&lt;/${tag}><img src=x onerror=alert(1)>--></template></${tag}>`,
);

const reparsedDoc = domino.createDocument('<body>' + serialized + '</body>');
reparsedDoc.getElementsByTagName('img').length.should.equal(0);

const reparsed = reparsedDoc.body.innerHTML;
reparsed.should.not.containEql(`</${tag}><img`);
const alerted = await alertFired(reparsed);
alerted.should.equal(
false,
`alert fired after normal HTML reparse for template comment in <${tag}>: ` + reparsed,
);
}
}
};

exports.fallbackRawTextProcessingInstructionEscapesAncestorClosingTag = async function () {
const fallbackTags = ['noscript', 'iframe', 'noembed', 'noframes'];

for (const tag of fallbackTags) {
// noscript/iframe/noembed/noframes > ProcessingInstruction
{
const document = domino.createDocument('');
const fallbackEl = document.createElement(tag);
fallbackEl.appendChild(document.createProcessingInstruction('x', `</${tag}><img src=x onerror=alert(1)>`));
document.body.appendChild(fallbackEl);

const serialized = document.body.serialize();
serialized.should.equal(
`<${tag}><?x &lt;/${tag}&gt;<img src=x onerror=alert(1)&gt;?></${tag}>`,
);

const reparsedDoc = domino.createDocument('<body>' + serialized + '</body>');
reparsedDoc.getElementsByTagName('img').length.should.equal(0);

const reparsed = reparsedDoc.body.innerHTML;
reparsed.should.not.containEql(`</${tag}><img`);
const alerted = await alertFired(reparsed);
alerted.should.equal(
false,
`alert fired after normal HTML reparse for PI in <${tag}>: ` + reparsed,
);
}

// noscript/iframe/noembed/noframes > template > ProcessingInstruction
{
const document = domino.createDocument('');
const fallbackEl = document.createElement(tag);
const template = document.createElement('template');
template.content.appendChild(document.createProcessingInstruction('x', `</${tag}><img src=x onerror=alert(1)>`));
fallbackEl.appendChild(template);
document.body.appendChild(fallbackEl);

const serialized = document.body.serialize();
serialized.should.equal(
`<${tag}><template><?x &lt;/${tag}&gt;<img src=x onerror=alert(1)&gt;?></template></${tag}>`,
);

const reparsedDoc = domino.createDocument('<body>' + serialized + '</body>');
reparsedDoc.getElementsByTagName('img').length.should.equal(0);

const reparsed = reparsedDoc.body.innerHTML;
reparsed.should.not.containEql(`</${tag}><img`);
const alerted = await alertFired(reparsed);
alerted.should.equal(
false,
`alert fired after normal HTML reparse for template PI in <${tag}>: ` + reparsed,
);
}
}
};

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