CVE-2026-83618: xmldom: requireWellFormed DocType publicId/systemId validation is bypassable via an embedded line terminator

An embedded line terminator bypasses the requireWellFormed serializer check for a DocumentType’s publicId and systemId. The check was added to fix GHSA-f6ww-3ggp-fr8h; an id whose first line is a valid literal slips past it and is emitted verbatim into the <!DOCTYPE …> declaration, so the markup after the line terminator breaks out into the surrounding document. Callers who enabled requireWellFormed to neutralize DocumentType injection remain exposed.