Server-Side Request Forgery (SSRF) vulnerability in Keycloak due to improper handling of HTTP redirects during client configuration processing. The flaw arises because Keycloak follows redirect responses (e.g., HTTP 302) without validating the final destination URL. An attacker can supply a crafted sector_identifier_uri that initially matches allowed patterns but redirects to internal resources such as cloud metadata endpoints (e.g., 169.254.169.254). This causes Keycloak to issue unintended requests from its network context, enabling blind SSRF. The vulnerability can be exploited remotely without authentication or user interaction, allowing attackers to perform internal network reconnaissance and potentially access sensitive information.