Deserialization of untrusted data

SharedSecretClusterAuthenticator in Atlassian Bitbucket Data Center versions 5.14.0 and later before 7.6.14, 7.7.0 and later prior to 7.17.6, 7.18.0 and later prior to 7.18.4, 7.19.0 and later prior to 7.19.4, and 7.20.0 allow a remote, unauthenticated attacker to execute arbitrary code via Java deserialization.