[org.jenkins-ci.plugins:cas-plugin] Open redirect vulnerability in Jenkins CAS Plugin

CAS Plugin 1.6.0 and earlier improperly determines that a redirect URL after login is legitimately pointing to Jenkins.

This allows attackers to perform phishing attacks by having users go to a Jenkins URL that will forward them to a different site after successful authentication.

CAS Plugin 1.6.1 only redirects to relative (Jenkins) URLs.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-21673
• https://www.jenkins.io/security/advisory/2021-06-30/#SECURITY-2387
• http://www.openwall.com/lists/oss-security/2021/06/30/1
• https://github.com/advisories/GHSA-2vvr-5757-qp87