<Issue Description> Spring Security OAuth versions 2.5.x prior to 2.5.2 and older unsupported versions are susceptible to a Denial-of-Service (DoS) attack via the initiation of the Authorization Request in an OAuth 2.0 Client application. A malicious user or attacker can send multiple requests initiating the Authorization Request for the Authorization Code Grant, which has the potential of exhausting system resources using a single session. This vulnerability exposes OAuth 2.0 Client applications only.
When processing authorization requests using the whitelabel views in Spring Security OAuth 2.0.0 to 2.0.9 and 1.0.0 to 1.0.5, the response_type parameter value was executed as Spring SpEL which enabled a malicious user to trigger remote code execution via the crafting of the value for response_type.