An issue has been discovered in GitLab EE affecting all versions starting from 14.2 before 15.9.6, all versions starting from 15.10 before 15.10.5, all versions starting from 15.11 before 15.11.1. Lack of verification on RelayState parameter allowed a maliciously crafted URL to obtain access tokens granted for 3rd party Group SAML SSO logins. This feature isn't enabled by default.
https://hackerone.com/reports/1923672
https://gitlab.com/gitlab-org/gitlab/-/issues/406235
https://gitlab.com/gitlab-org/cves/-/blob/master/2023/CVE-2023-1965.json