xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) "DOMParser" and "XMLSerializer" module. In xmldom versions 0.6.0 and prior and @xmldom/xmldom prior to versions 0.8.12 and 0.9.9, xmldom/xmldom allows attacker-controlled strings containing the CDATA terminator ]]> to be inserted into a CDATASection node. During serialization, XMLSerializer emitted the CDATA content verbatim without rejecting or safely splitting the terminator. As a result, data intended to remain text-only became active XML markup in the serialized output, enabling XML structure injection and downstream business-logic manipulation. This issue has been patched in xmldom version 0.6.0 and @xmldom/xmldom versions 0.8.12 and 0.9.9.