GeoNetwork's post-login redirect handling can be bypassed to redirect users to an attacker-controlled external site, even though the code attempts to restrict redirect targets to relative, in-application URLs. This affects both supported SSO login methods: OAuth2/OIDC and Keycloak.
It is possible to craft a URL that causes GeoNetwork to reflect attacker-controlled content into an error page in a way that gets evaluated as a client-side template expression. Combined with known AngularJS sandbox-escape techniques, this can be used to execute arbitrary JavaScript in the victim's browser (reflected Cross-Site Scripting via client-side template injection).
GeoNetwork's Elasticsearch-backed search API is responsible for injecting access-control and visibility filters into every request before it reaches the underlying Elasticsearch index. Under certain request conditions, that filtering step does not run, allowing an unauthenticated user to retrieve indexed metadata records that should be restricted, including records limited to specific groups.