chore(deps): update dependency @xmldom/xmldom@<0.8.12 to v0.8.13 [security]#4434
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This PR contains the following updates:
0.8.12→0.8.13xmldom has XML node injection through unvalidated processing instruction serialization
CVE-2026-41675 / GHSA-x6wf-f3px-wcqx
More information
Details
Summary
The package allows attacker-controlled processing instruction data to be serialized into XML without validating or neutralizing the PI-closing sequence
?>. As a result, an attacker can terminate the processing instruction early and inject arbitrary XML nodes into the serialized output.Details
The issue is in the DOM construction and serialization flow for processing instruction nodes.
When
createProcessingInstruction(target, data)is called, the supplieddatastring is stored directly on the node without validation. Later, when the document is serialized, the serializer writes PI nodes by concatenating<?, the target, a space,node.data, and?>directly.That behavior is unsafe because processing instructions are a syntax-sensitive context. The closing delimiter
?>terminates the PI. If attacker-controlled input contains?>, the serializer does not preserve it as literal PI content. Instead, it emits output where the remainder of the payload is treated as live XML markup.The same class of vulnerability was previously addressed for CDATA sections (GHSA-wh4c-j3r5-mjhp / CVE-2026-34601), where
]]>in CDATA data was handled by splitting. The serializer applies no equivalent protection to processing instruction data.Affected code
lib/dom.js—createProcessingInstruction(lines 2240–2246):No validation is performed on
data. Any string including?>is stored as-is.lib/dom.js— serializer PI case (line 2966):node.datais emitted verbatim. If it contains?>, that sequence terminates the PI in the outputstream and the remainder appears as active XML markup.
Contrast — CDATA (line 2945, patched):
PoC
Minimal (from @tlsbollei report, 2026-04-01)
With re-parse verification (from @tlsbollei report)
Impact
An application that uses the package to build XML from untrusted input can be made to emit attacker-controlled elements outside the intended PI boundary. That allows the attacker to alter the meaning and structure of generated XML documents.
In practice, this can affect any workflow that generates XML and then stores it, forwards it, signs it, or hands it to another parser. Realistic targets include XML-based configuration, policy documents, and message formats where downstream consumers trust the serialized structure.
As noted by @tlsbollei: this is the same delimiter-driven XML injection bug class previously addressed by GHSA-wh4c-j3r5-mjhp for
createCDATASection(). Fixing CDATA while leaving PI creation and PI serialization unguarded leaves the same standards-constrained issue open for another node type.Disclosure
This vulnerability was publicly disclosed at 2026-04-06T11:25:07Z via
xmldom/xmldom#987, which was subsequently closed
without being merged.
Fix Applied
XMLSerializer.serializeToString()now accepts an options object as a second argument. When{ requireWellFormed: true }is passed, the serializer throwsInvalidStateErrorbefore emitting any ProcessingInstruction node whose.datacontains?>. This check applies regardless of how?>entered the node — whether viacreateProcessingInstructiondirectly or a subsequent mutation (.data =,CharacterDatamethods).On
@xmldom/xmldom≥ 0.9.10, the serializer additionally applies the full W3C DOM Parsing §3.2.1.7 checks whenrequireWellFormed: true:InvalidStateErrorif the PI target contains a:character or is an ASCII case-insensitive match for"xml".InvalidStateErrorif the PI data contains characters outside the XML Char production.InvalidStateErrorif the PI data contains?>.On
@xmldom/xmldom≥ 0.8.13 (LTS), only the?>data check (check 3) is applied. The target and XML Char checks are not included in the LTS fix.PoC — fixed path
The guard catches
?>regardless of when it was introduced:Why the default stays verbatim
The W3C DOM Parsing and Serialization spec §3.2.1.3 defines a
require well-formedflag whose default value isfalse. With the flag unset, the spec explicitly permits serializing PI data verbatim. This matches browser behavior: Chrome, Firefox, and Safari all emit?>in PI data verbatim by default without error.Unconditionally throwing would be a behavioral breaking change with no spec justification. The opt-in
requireWellFormed: trueflag allows applications that require injection safety to enable strict mode without breaking existing code.Residual limitation
createProcessingInstruction(target, data)does not validatedataat creation time. The WHATWG DOM spec (§4.5 step 2) mandates anInvalidCharacterErrorwhendatacontains?>; enforcing this check unconditionally at creation time is a breaking change and is deferred to a future breaking release.When the default serialization path is used (without
requireWellFormed: true), PI data containing?>is still emitted verbatim. Applications that do not passrequireWellFormed: trueremain exposed.Severity
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
xmldom has XML injection through unvalidated DocumentType serialization
CVE-2026-41674 / GHSA-f6ww-3ggp-fr8h
More information
Details
Summary
The package serializes
DocumentTypenode fields (internalSubset,publicId,systemId) verbatimwithout any escaping or validation. When these fields are set programmatically to attacker-controlled
strings,
XMLSerializer.serializeToStringcan produce output where the DOCTYPE declaration isterminated early and arbitrary markup appears outside it.
Details
DOMImplementation.createDocumentType(qualifiedName, publicId, systemId, internalSubset)validatesonly
qualifiedNameagainst the XML QName production. The remaining three arguments are storedas-is with no validation.
The XMLSerializer emits
DocumentTypenodes as:All fields are pushed into the output buffer verbatim — no escaping, no quoting added.
internalSubsetinjection: The serializer wrapsinternalSubsetwith[and]. A valuecontaining
]>closes the internal subset and the DOCTYPE declaration at the injection point.Any content after
]>ininternalSubsetappears outside the DOCTYPE in the serialized output asraw XML markup. Reported by @TharVid (GHSA-f6ww-3ggp-fr8h). Affected:
@xmldom/xmldom≥ 0.9.0via
createDocumentTypeAPI; 0.8.x only via direct property write.publicIdinjection: The serializer emitspublicIdverbatim afterPUBLICwith noquoting added. A value containing an injected system identifier (e.g.,
"pubid" SYSTEM "evil") breaks the intended quoting context, injecting a fake SYSTEM entryinto the serialized DOCTYPE declaration. Identified during internal security research. Affected:
both branches, all versions back to 0.1.0.
systemIdinjection: The serializer emitssystemIdverbatim. A value containing>terminates the DOCTYPE declaration early; content after
>appears as raw XML markup outsidethe DOCTYPE context. Identified during internal security research. Affected: both branches, all
versions back to 0.1.0.
The parse path is safe: the SAX parser enforces the
PubidLiteralandSystemLiteralgrammarproductions, which exclude the relevant characters, and the internal subset parser only accepts a
subset it can structurally validate. The vulnerability is reachable only through programmatic
createDocumentTypecalls with attacker-controlled arguments.Affected code
lib/dom.js—createDocumentType(lines 898–910):lib/dom.js— serializer DOCTYPE case (lines 2948–2964):PoC
internalSubset injection
publicId quoting context break
systemId injection
Impact
An application that programmatically constructs
DocumentTypenodes from user-controlled data andthen serializes the document can emit a DOCTYPE declaration where the internal subset is closed
early or where injected SYSTEM entities or other declarations appear in the serialized output.
Downstream XML parsers that re-parse the serialized output and expand entities from the injected
DOCTYPE declarations may be susceptible to XXE-class attacks if they enable entity expansion.
Fix Applied
XMLSerializer.serializeToString()now accepts an options object as a second argument. When{ requireWellFormed: true }is passed, the serializer validates theDocumentTypenode'spublicId,systemId, andinternalSubsetfields before emitting the DOCTYPE declaration and throwsInvalidStateErrorif any field contains an injection sequence:publicId: throws if non-empty and does not match the XMLPubidLiteralproduction (XML 1.0 [12])systemId: throws if non-empty and does not match the XMLSystemLiteralproduction (XML 1.0 [11])internalSubset: throws if it contains]>(which closes the internal subset and DOCTYPE declaration early)All three checks apply regardless of how the invalid value entered the node — whether via
createDocumentTypearguments or a subsequent direct property write.PoC — fixed path
The guard also covers post-creation property writes:
Why the default stays verbatim
The W3C DOM Parsing and Serialization spec §3.2.1.3 defines a
require well-formedflag whose default value isfalse. With the flag unset, the spec permits verbatim serialization of DOCTYPE fields. Unconditionally throwing would be a behavioral breaking change with no spec justification. The opt-inrequireWellFormed: trueflag allows applications that require injection safety to enable strict mode without breaking existing deployments.Residual limitation
createDocumentType(qualifiedName, publicId, systemId[, internalSubset])does not validatepublicId,systemId, orinternalSubsetat creation time. This creation-time validation is a breaking change and is deferred to a future breaking release.When the default serialization path is used (without
requireWellFormed: true), all three fields are still emitted verbatim. Applications that do not passrequireWellFormed: trueremain exposed.Severity
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
xmldom has XML node injection through unvalidated comment serialization
CVE-2026-41672 / GHSA-j759-j44w-7fr8
More information
Details
Summary
The package allows attacker-controlled comment content to be serialized into XML without validating or neutralizing comment breaking sequences. As a result, an attacker can terminate the comment early and inject arbitrary XML nodes into the serialized output.
Details
The issue is in the DOM construction and serialization flow for comment nodes.
When
createComment(data)is called, the supplied string is stored as comment data through the generic character-data handling path. That content is kept as-is. Later, when the document is serialized, the serializer writes comment nodes by concatenating the XML comment delimiters with the storednode.datavalue directly.That behavior is unsafe because XML comments are a syntax-sensitive context. If attacker-controlled input contains a sequence that closes the comment, the serializer does not preserve it as literal comment text. Instead, it emits output where the remainder of the payload is treated as live XML markup.
This is a real injection bug, not a formatting issue. The serializer already applies context-aware handling in other places, such as escaping text nodes and rewriting unsafe CDATA terminators. Comment content does not receive equivalent treatment. Because of that gap, untrusted data can break out of the comment boundary and modify the structure of the final XML document.
PoC
Impact
An application that uses the package to build XML from untrusted input can be made to emit attacker-controlled elements outside the intended comment boundary. That allows the attacker to alter the meaning and structure of generated XML documents.
In practice, this can affect any workflow that generates XML and then stores it, forwards it, signs it, or hands it to another parser. Realistic targets include XML-based configuration, policy documents, and message formats where downstream consumers trust the serialized structure.
Disclosure
This vulnerability was publicly disclosed at 2026-04-06T11:25:07Z via xmldom/xmldom#987, which was subsequently closed without being merged.
Fix Applied
XMLSerializer.serializeToString()now accepts an options object as a second argument. When{ requireWellFormed: true }is passed, the serializer throwsInvalidStateErrorbefore emitting a Comment node whose.datawould produce malformed XML.On
@xmldom/xmldom≥ 0.9.10, the full W3C DOM Parsing §3.2.1.4 check is applied: throws if.datacontains--anywhere, ends with-, or contains characters outside the XML Char production.On
@xmldom/xmldom≥ 0.8.13 (LTS), only the-->injection sequence is checked. The0.8.xSAX parser accepts comments containing--(without>), so throwing on bare--would break a previously-working round-trip on that branch. The-->check is sufficient to prevent injection.PoC — fixed path
Why the default stays verbatim
The W3C DOM Parsing and Serialization spec §3.2.1.4 defines a
require well-formedflag whose default value isfalse. With the flag unset, the spec explicitly permits serializing ill-formed comment content verbatim — this is also the behavior of browser implementations (Chrome, Firefox, Safari):new XMLSerializer().serializeToString(doc)produces the injection sequence without error in all major browsers.Unconditionally throwing would be a behavioral breaking change with no spec justification. The opt-in
requireWellFormed: trueflag allows applications that require injection safety to enable strict mode without breaking existing deployments.Residual limitation
The fix operates at serialization time only. There is no creation-time check in
createComment— the spec does not require one for comment data. Any path that leads to a Comment node with--in its data (createComment,appendData,.data =, etc.) produces a node that serializes safely only when{ requireWellFormed: true }is passed toserializeToString.Severity
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
Release Notes
xmldom/xmldom (@xmldom/xmldom@<0.8.12)
v0.8.13Compare Source
Fixed
XMLSerializer.serializeToString()(andNode.toString(),NodeList.toString()) now accept arequireWellFormedoption (fourth argument, afterisHtmlandnodeFilter). When{ requireWellFormed: true }is passed, the serializer throwsInvalidStateErrorfor injection-prone node content, preventing XML injection via attacker-controlled node data.GHSA-j759-j44w-7fr8GHSA-x6wf-f3px-wcqxGHSA-f6ww-3ggp-fr8hdatacontains-->datacontains?>publicIdfailsPubidLiteral,systemIdfailsSystemLiteral, orinternalSubsetcontains]>XMLSerializer.serializeToString(),Node.prototype.normalize(),Node.prototype.cloneNode(true),Document.prototype.importNode(node, true),node.textContentgetter,getElementsByTagName()/getElementsByTagNameNS()/getElementsByClassName()/getElementById()) are now iterative. Previously, deeply nested DOM trees would exhaust the JavaScript call stack and throw an unrecoverableRangeError.GHSA-2v35-w6hq-6mfwThank you,
@Jvr2022,
@praveen-kv,
@TharVid,
@decsecre583,
@tlsbollei,
@KarimTantawey,
for your contributions
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