Bamboo 6.6 release notes
With Bamboo 6.6 we offer you a brand new user directories management mechanism. It significantly enhances remote user resources handling and is free of many known problems with LDAP and Crowd server synchronization. Moreover, user directories management is now consistent with other Atlassian products such as Jira, Confluence or Bitbucket Server. You're free to define any number of user directories (local, LDAP, external Jira, external Crowd) and configure them to fit your needs.
Bamboo 6.6 drops the feature to write to external Crowd. Since Bamboo 6.6 all external user directories are treated as read only.