There are 15 interface admins as per these links

https://en.wikipedia.org/wiki/Wikipedia:Interface_administra...

https://en.wikipedia.org/wiki/Special:ListUsers/interface-ad...

Those are the English Wikipedia-only users, but you also need to include the "global" users (which I think were the source of this specific compromise?). Search this page [0] for "editsitejs" to see the lists of global users with this permission.

[0]: https://en.wikipedia.org/wiki/Special:GlobalGroupPermissions