URL Redirection to Untrusted Site ('Open Redirect')

Summary

An open redirect vulnerability was found in Keycloak. A specially crafted URL can be constructed where the "referrer" and "referrer_uri" parameters are made to trick a user into visiting a malicious webpage. A trusted URL can trick users and automation into believing that the URL is safe when, in fact, it redirects to a malicious server. This issue can result in a victim inadvertently trusting the destination of the redirect, potentially leading to a successful phishing attack or other types of attacks. Once a crafted URL is made, it can be sent to a Keycloak admin via email, for example. This will trigger this vulnerability when the user visits the page and clicks the link. A malicious actor can use this to target users they know are Keycloak admins for further attacks. It may also be possible to bypass other domain-related security checks, such as supplying this as an OAuth redirect URI. The malicious actor can further obfuscate the "redirect_uri" using URL encoding to hide the text of the actual malicious website domain. This issue affects org.keycloak:keycloak-services versions 3.4.0.CR1 prior to 25.0.0.