We have started using 0.10.0 under load and found a few issues around the UI and impersonation.
The UI when trying to connect to nimbus will impersonate other users. Nimbus, by default allows impersonation and just outputs a warning message that it is allowed. We really should default to not allowing impersonation. having the authorizer configured by default does not hurt when running insecure because impersonation is not possible, but when security is enabled if someone forgets to set this config we are now insecure by default.
If you do set all of that up correctly the UI now can impersonate the wrong user when connecting to nimbus.
The UI decides which user to impersonate by pulling it from the request context. The requestContext is populated from the HttpRequest when assert-authorized-user is called. assert-authorized-user takes a topology-conf as a parameter. The only way to get this topology conf is to talk to nimbus, which will get the wrong user because the request context has not been populated yet.
This just because a huge pain for users who way too often will not be able to see pages on the UI.