The vulnerability stems from improper escaping of the 'label' query parameter in the UI rendering layer. Jenkins plugins typically use Jelly templates for view rendering, and reflected XSS in this context would occur when user-controlled input (like the 'label' parameter) is directly interpolated into HTML without proper escaping. The advisory explicitly identifies the 'label' parameter as the injection vector, and the lack of escaping in the report display functionality (handled by BuildMetricsReport/index.jelly) would be the logical location for this vulnerability. The confidence is high because the pattern matches standard Jenkins plugin XSS vulnerabilities and the advisory specifically calls out the parameter and lack of escaping.