Under Manage Jenkins >> Mange Old Data i get the following exception:

ConversionException: Refusing to unmarshal credentials for security reasons; see https://jenkins.io/redirect/class-filter/ ---- Debugging information ---- class : java.util.Optional required-type : java.util.Optional converter-type : hudson.util.XStream2$BlacklistedTypesConverter path : /project/builders/org.jenkinsci.plugins.octoperf.OctoperfBuilder/credentials line number : 16 -------------------------------, InstantiationError: null