Details
Description
Currently it is not allowed to extend the group everyone by putting it as member to another group. The other way is prevented as well (i.e. putting some group or user as member of the everyone group) as every other principal is by default member of everyone. Extending the everyone group would therefore lead to cycles. Although this is correctly prevented in the code (https://github.com/apache/jackrabbit/blob/adb1e79ae26aba5d068be56e5e9eb562344e5bb9/jackrabbit-core/src/main/java/org/apache/jackrabbit/core/security/user/GroupImpl.java#L156) this is not noticed by the called.
I would instead suggest to fail more loudly by throwing an exception or at least log a warning.