Checkstyle before 8.18 loads external DTDs by default.Referenceshttps://github.com/checkstyle/checkstyle/pull/6476https://github.com/checkstyle/checkstyle/issues/6474https://github.com/checkstyle/checkstyle/issues/6478https://checkstyle.org/releasenotes.html#Release_8.18https://lists.apache.org/thread.html/7eea10e7be4c21060cb1e79f6524c6e6559ba833b1465cd2870a56b9%40%3Cserver-dev.james.apache.org%3Ehttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AEYBAHYAV37WHMOXZYM2ZWF46FHON6YC/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VJPT54USMGWT3Y6XVXLDEHKRUY2EI4OE/https://lists.debian.org/debian-lts-announce/2019/04/msg00029.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BMOPJ2XYE4LB2HM7OMSUBBIYEDUTLWE/https://lists.apache.org/thread.html/a35a8ccb316d4c2340710f610cba8058e87d5376259b35ef3ed2bf89%40%3Cnotifications.accumulo.apache.org%3Ehttps://lists.apache.org/thread.html/fff26ee7b59360a0264fef4e8ed9454ef652db2c39f2892a9ea1c9cb%40%3Cnotifications.fluo.apache.org%3Ehttps://lists.apache.org/thread.html/6bf8bbbca826e883f09ba40bc0d319350e1d6d4cf4df7c9e399b2699%40%3Ccommits.fluo.apache.org%3Ehttps://lists.apache.org/thread.html/994221405e940e148adcfd9cb24ffc6700bed70c7820c55a22559d26%40%3Cnotifications.fluo.apache.org%3Ehttps://lists.apache.org/thread.html/rda99599896c3667f2cc9e9d34c7b6ef5d2bbed1f4801e1d75a2b0679%40%3Ccommits.nifi.apache.org%3E
