If some jobs have been run with a version < 1.40.0, they are still affected by https://www.jenkins.io/security/advisory/2018-03-26/#SECURITY-261, so it's quite hard to know if we're at risk or not (apart from running https://github.com/jenkinsci-cert/SECURITY-261 on a regular basis).
Also, the plugin is for adoption and advise to switch to https://plugins.jenkins.io/github-branch-source/ which is preferable anyway.
@fredg02, what do you think?