Jan Monterrubio
added a comment - I cloned the linked repository and updated to the 2.277.2 version of the war and I was able to save a white list target: https://github.com/jenkinsci/ghprb-plugin/blob/1064dfb278d95ea6bad3a419a032cdb5122bb261/src/main/resources/org/jenkinsci/plugins/ghprb/GhprbTrigger/config.groovy#L59
I cloned the linked repository and updated to the 2.277.2 version of the war and I was able to save a white list target: https://github.com/jenkinsci/ghprb-plugin/blob/1064dfb278d95ea6bad3a419a032cdb5122bb261/src/main/resources/org/jenkinsci/plugins/ghprb/GhprbTrigger/config.groovy#L59