Probably as a result of https://jenkins.io/security/advisory/2018-09-25/#SECURITY-1130 the plugin has started displaying configuration files improperly escaped, i.e. replacing XML entities where it should not, e.g.:

I first found this in our CI environment and thought maybe this was an issue in our end with the server configuration, but then I tried installing the plugin in a fresh Docker container (based on the jenkins/jenkins:lts image) and the issue reproduces there.