Hello Daemien,
What I can say... WebEx is not following any standard so you need to customize attributes and their delclaration.
We have customers who are using WebEx but I can't copy-paste their configuration in public forum. If you want it badly, we can create one generic doc and publish.
[Here](https://support.gluu.org/single-sign-on/3005/map-external-ldap-source-attribute-to-two-attributes-in-gluu-ldap/) is an associated ticket.