The package serializes DocumentType node fields (internalSubset, publicId, systemId) verbatim
without any escaping or validation. When these fields are set programmatically to attacker-controlled
strings, XMLSerializer.serializeToString can produce output where the DOCTYPE declaration is
terminated early and arbitrary markup appears outside it.
DOMImplementation.createDocumentType(qualifiedName, publicId, systemId, internalSubset) validates
only qualifiedName against the XML QName production. The remaining three arguments are stored
as-is with no validation.
The XMLSerializer emits DocumentType nodes as:
<!DOCTYPE name[ PUBLIC pubid][ SYSTEM sysid][ [internalSubset]]>
All fields are pushed into the output buffer verbatim — no escaping, no quoting added.
internalSubset injection: The serializer wraps internalSubset with [ and ]. A value
containing ]> closes the internal subset and the DOCTYPE declaration at the injection point.
Any content after ]> in internalSubset appears outside the DOCTYPE in the serialized output as
raw XML markup. Reported by @TharVid (GHSA-f6ww-3ggp-fr8h). Affected: @xmldom/xmldom ≥ 0.9.0
via createDocumentType API; 0.8.x only via direct property write.
publicId injection: The serializer emits publicId verbatim after PUBLIC with no
quoting added. A value containing an injected system identifier (e.g.,
"pubid" SYSTEM "evil") breaks the intended quoting context, injecting a fake SYSTEM entry
into the serialized DOCTYPE declaration. Identified during internal security research. Affected:
both branches, all versions back to 0.1.0.
systemId injection: The serializer emits systemId verbatim. A value containing >
terminates the DOCTYPE declaration early; content after > appears as raw XML markup outside
the DOCTYPE context. Identified during internal security research. Affected: both branches, all
versions back to 0.1.0.
The parse path is...
0.8.130.9.10Exploitability
AV:NAC:LAT:NPR:NUI:NVulnerable System
VC:NVI:HVA:NSubsequent System
SC:NSI:NSA:N8.7/CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N