xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. In @xmldom/xmldom prior to versions 0.9.10 and 0.8.13 and xmldom version 0.6.0 and prior, 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.

This issue has been patched in versions @xmldom/xmldom versions 0.9.10 and 0.8.13.