Actually, Gluu is not yet 20 years old company so none of our customers or we ever faced this issue yet. Here is another screenshot of a default installation of 4.2.3 attached.
However, this is a good point... "How to update OpenDJ certificate". And, you can start with [this](https://backstage.forgerock.com/knowledge/kb/article/a72105266) doc.
May be in future, if required we will publish a doc publicly on how to renew WrenDS certificate inside Gluu Server.