A flaw was found in the SAML client registration in Keycloak that could allow an administrator to register malicious JavaScript URIs as Assertion Consumer Service POST Binding URLs (ACS), posing a Cross-Site Scripting (XSS) risk. This issue may allow a malicious admin in one realm or a client with registration access to target users in different realms or applications, executing arbitrary JavaScript in their contexts upon form submission. This can enable unauthorized access and harmful actions, compromising the confidentiality, integrity, and availability of the complete KC instance.

A flaw was found in Keycloak's OIDC component in the "checkLoginIframe," which allows unvalidated cross-origin messages. This flaw allows attackers to coordinate and send millions of requests in seconds using simple code, significantly impacting the application's availability without proper origin validation for incoming messages.

A vulnerability was found in the quarkus-core component. Quarkus captures local environment variables from the Quarkus namespace during the application's build, therefore, running the resulting application inherits the values captured at build time. Some local environment variables may have been set by the developer or CI environment for testing purposes, such as dropping the database during application startup or trusting all TLS certificates to accept self-signed certificates. If these properties are configured using environment variables or the .env facility, they are captured into the built application, which can lead to dangerous behavior if the application does not override these values. This behavior only happens for configuration properties from the `quarkus.*` namespace. Application-specific properties are not captured.