Similar situation here: https://sritest.io/#report/c41dbd04-6e3b-4bfe-a13a-7eb8a1c8defe
and https://observatory.mozilla.org/analyze.html?host=tubejack.nl
check plug-ins for updates: https://hackertarget.com/wordpress-security-scan/
vulnerable jQuery library: http://retire.insecurity.today/#!/scan/1d8a69f8ab84fd0e4b8c2efd92aca53670608f2a806637efed09886511b99296
various sources and sinks: http://www.domxssscanner.com/scan?url=https%3A%2F%2Ftubejack.nl
Have to add this vulnerability there also: http://retire.insecurity.today/#!/scan/792275039ee53608d3f656d266e6b46883f317296c274d25d795e0104b9167ab

polonus