An incorrect permission check in Jenkins GitLab Plugin 1.9.6 and earlier allows attackers with global Item/Configure permission (while lacking Item/Configure permission on any particular job) to enumerate credential IDs of GitLab API token and Secret text credentials stored in Jenkins.
Jenkins GitLab Plugin 1.5.35 and earlier uses a non-constant time comparison function when checking whether the provided and expected webhook token are equal, potentially allowing attackers to use statistical methods to obtain a valid webhook token.